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I think you are onto something Azaghal.  However as the Elves are not prone to Illness, Sickness or Disease (or disorders I imagine)  its far more likely that he was touched by the Evil, Hate and Anger of Morgoth.  Who knows, as Morgoth hated Feanor more than any other Elf, perhaps he found a way of afflicting him with some unknown new thing.  He and Sauron managed to create plague like diseases which effected Men in later ages.

There is a heap on Feanor in other threads, take a look ibn the characters section.

If he did have such an illness it would have quickly come to the attention of Eru and those of the mighty ones and they would surely have had the means to deal with the problem to the joy of all . But to me, most likely it was selfish decisions and dark thoughts that caused darkness and evil to lodge in his heart. The choices we all have to make daily of good and evil, and he chose the later.

My thoughts are similar to what Brego - what for us might be some kind of mental illness, in the Tolkien universe is probably one of many aspects of evil spread by Morgoth on Arda. Feanor's behaviour definitely is something we didn't see before him - I'd say he is showing that particular dark side. It's like seven sins in the Catholic religion - they are all different aspect to the same thing.

Ive mentioned before in other threads and sorry to repeat myself.  I think there is something important in the demise of Feanor's dear mother Miriel.  I have a suspicion that somehow (I dont know how) Morgoth managed to do something to her, which effected Feanor before his birth.  I know that Morgoth was in the Fastness of Mandos during this time, but perhaps he found a way to infect or alter, using his great power, the Noldorian Queen, the first Elf to die in The Undying lands. As a Valar, he had great foresight and perhaps knew of the doom of Feanor and actually caused it in the first place.  A master stroke of Evil. Also by coincidence, Miriel's spirit would have been housed in Mandos, at the same time as Melkor was imprisoned there. I'm sure in a different area, but still in his halls,

I would not say that Morgoth did anything to Miriel specifically while he was imprisoned.

The idea however (see Finwe and Miriel 4, Morgoth's Ring), is that Elvish bodies were made of the stuff of Arda, which contained a Melkor ingredient. Morgoth invested his power into the very 'physical constituents of the Earth' and thus 'the whole of Middle-earth was Morgoth's Ring' 

In this way Morgoth's evil 'entered' into Aman and was in a very general sense a part of Miriel's fate; and I cannot help but note the singular circumstances of Feanor's birth here -- as Nerdanel, for example, had seven sons while Miriel was wearied beyond the desire for life from having Feanor alone.


Like him or not, Feanor was very great, drawing so much from his mother that she was wearied beyond healing, her hroa made of the stuff of Arda (itself tainted by Melkor in the days of his might).

I cannot believe that Illuvatar would have deliberately created a great, good and powerful being, and then allow him to suck the life energy from his Mother to the point of deliberate body abandonment, resulting in all the evil things to them play out from this one act.  I just cant see it. 

'But in the bearing of her son Miriel was consumed in spirit and body; and after his birth she yearned for release from the labour of living.'



That is the reason Miriel desired to die. And (for better clarity):

'Also the Eldar say that in the begetting, and still more in the bearing of children, greater share and strength of their being, in mind and in body, goes forth than in the making of mortal children.'

Laws And Customs of the Eldar, Morgoth's Ring

My 'drawing' above was just another way to say this. A great Elf given a notably different circumstance regarding his birth.


I totally agree with Brego in the first post here. Morgoth hated so much to Feanor that perhaps with some kind of power could turned him to be such a character. We must never forget how the ring made Frodo a completely distrustful being! He became a dark ghost as days went by.  When evil is against you, its will can turn you in the most hateful being if you are not strong.

It happens the same in real life, what does it happen when a cheerful person works or is the whole day with moaners that only see the glass half empty? You come into this negative spiral and go down and down until no one can recognize you!

Keep in mind too Feanor's attitude toward Morgoth, and his [Feanor's] way of working:

'... for none of the Eldalie ever hated Melkor more than Feanor son of Finwe, who first named him Morgoth; and snared though he was in the webs of Melkor's malice against the Valar he held no converse with him and took no counsel from him. For Feanor was driven by the fire of his own heart only, working ever swiftly and alone; and...'

And after Feanor crafted the Silmarils, Morgoth: 'From that time forth, inflamed by this desire, he sought ever more eagerly how he should destroy Feanor and end the Friendship of the Valar and the Elves.'

Brego in his first post writes: 'Who knows, as Morgoth hated Feanor more than any other Elf, perhaps he found a way of afflicting him with some unknown new thing. He and Sauron managed to create plague like diseases which effected Men in later ages.' 

But Melkor sowed lies rather than some unknown new thing or disease, if subtly; and conjured visions (in the hearts of the Elves) of mighty realms that they could have ruled at their own will; and by this poisoning (among other lies) he reached Feanor indirectly, for Feanor burned with a desire for wider realms and 'freedom' from the Valar.

Generally speaking this wasn't only something Feanor felt, for even though Galadriel swore no oath, she too (at least) 'yearned to see the wide unguarded lands and to rule there a realm of her own', kindled by the words of Feanor himself.

Of like mind with Galadriel was Fingon, also being moved by Feanor, as well as others of the Noldor, kindled with the desire of new things and strange countries.

Ok, then we might think that maybe Feanor has no disease but he was the first Elf that felt hatred. I don't remember the elves hating Melkor, only being scared of him.  He used lies to get his own purposes, so malice appeared in his heart. He defied the Valar, had a boastful behaviour and I think at first, he really wanted revenge and get back the Silmarils, but at the end it was more a matter of ego than a true desire of making justice.

Feanor is not one of my favourite characters... Sorry.

What happened to Muriel is not even an uncommon happening today. Because the babe in the womb has to get its nourishment from mummy it occurs at times that the mother seems literally sucked dry in body and consequently in spirit because of the horrible drain so that she may want to just die. This in fact happened to me personally with the birth of my second son, but the first to live. I was having a strange and gradually worsening pregnancy. in the first trimester i had a mild stroke and had to be in a blackened room in the hospital and could not speak and every one whispered around me in case my blood pressure should shoot up.

Things got worse and worse and they had to fly a specialist (heart) in to help me bring my son into the world. I had so many doctors and nurses it was beyond belief. After the birth he seemed unnaturally hungry and he just seemed to take every bit of my strength with each feeding. I was very attached to him, but after about four months i remember clearly having no more strength to fight and just wanting to be released and die. A tough Scottish nurse told me sternly I would surely die if I did not fight. So I was transferred to a Swedish Herbalist who concurred that I was near death and that my son was literally draining me of nutrients and such. I was given treatments over a year and it took two years to recover. My poor little one had to have a bottle instead but slowly I recovered. So, even without any Melkorian shananigans these things can happen. I think that with one at least, perhaps baby John Tolkien, Edith went through a similar horror before things got better.

Leelee, a remarkable story of the strength of Women. Women in general put Men to shame in the strength of mind and body. This is repeated also throughout the animal kingdom as well. There are many a tale of the strength of Mothers in peril and their remarkable abilities of body and soul. I'll say this also about Feanor and Milriel. I still think that a seed of hate or doom was planted in either Miriel and or Finwe very early on, perhaps even as far back as their Awakening to set the entire Doom of the Noldor. We know that Melkor sent his spies amongst the newly awakened Elves in Cuivienen. Maybe a curse was put upon them or within one of them. A curse laid out to work slowly over thousands of years, its ultimate goal, to ruin the purity of the Elves and to ruin another of the Vala's plans.

Elbereth wrote: Ok, then we might think that maybe Feanor has no disease but he was the first Elf that felt hatred.

I won't quibble with the word hatred here, but I'll add that Tolkien does note bitterness among his Elves even before Feanor was born for example [for instance, however taken out of context here for sake of brevity: 'This ill-feeling descended in part from the bitterness of the Debate before the March of the Eldar began, and was no doubt later increased by the machinations of Morgoth' JRRT, Quendi And Eldar, The War of the Jewels]

And Melkor had cozened many of the Noldor before Feanor had reason to 'hate' Morgoth specifically: the Silmarillion notes that many of the Noldor leaned towards Melkor, and (noted later) that the Noldor even began to murmur against the Valar, many becoming filled with pride.

Yes Feanor was among them at this time, but the Silmarillion relates that Morgoth had kindled the hearts of the Noldor to strife, and of their quarrels came at length the end of the High Days of Valinor. Feanor was the first to speak 'openly' against the Valar, and so at first the Valar guessed that he was behind the discontent. 

But ultimately Melkor came to Feanor at Formenos, and Feanor pondered 'if indeed he might yet trust him so far as to aid him in his flight' -- but Morgoth overreached himself and awoke a fire more fierce than he designed, and Feanor then pierced 'the cloaks of his mind' [Melkor's mind] and found there Morgoth's lust for the Silmarils. 'Then hate overcame Feanor's fear...'

And the subsequent slaying of Finwe and theft of the Silmarils... well that didn't help


In any case, one need not imagine Melkor, while captive, doing something to Miriel and Finwe, nor that Morgoth cursed them in Middle-earth before his captivity.

Judging from an earlier post, Brego appears to think so (although I assume it's one or the other at this point, not both] because he finds something problematic with Tolkien's God Eru 'allowing' something, and so Melkor is injected in a way that Tolkien did not employ him.

In my opinion the story needs none of this however. To my mind all one need do is embrace Tolkien's notion of God, Free Will, and Arda Marred, and there is no reason for Morgoth to be cursing Finwe and Miriel before her desire to die. And the author can be quite clear when he wants the reader to imagine a specific curse upon a given person or family -- thinking Hurin, for example.


For the debate of the Valar regarding the case of Finwe and Miriel, see Laws And Customs of the Eldar, Morgoth's Ring. And for an interesting statement from Miriel...

'My life has gone out into Feanor, my son. That gift I have given to him whom I loved. I can give no more. Beyond Arda this may be healed, but not within it.'

JRRT, Finwe And Miriel, version 4, Of The Silmarils And The Darkening Of Valinor, [subtitle Of Finwe And Miriel], Morgoth's Ring

Bitterness is a key element it seems in many of the tales told. It appears that the music of Illuvatar, perfect, beyond beautiful and saturated with truth and splendor, was quickly thinned into a weakened version by the works of Illuvatars enemies, thereby creating different takes on His Truth in the lives of every creation.

So, what was just and truthful to one might be treason and unfair advantage to another. This, plus the rock hard sticking together of clans in some instances would be reason enough for bitterness to grow silently in the heart until the cup had overflowed and tragedy the result. It is all so tiring and that is the sense i got so many times as I read the stories.

Just now reading Leelee's comment and thinking about music I do believe that J.R.R might have been the first to think of the string theory

Azaghal I kind of agree, however I think the Elves were originally created pure and perfect. But as far back as The Music of creation Melkor was effecting the outcome of their being. I also believe however that Melkor's actions were actually planned or at least allowed by Iluvatar. Iluvatar at any time could have put a stop to Melkor's plan for domination. Iluvatar showed the Valar and Ainur a vision of a perfect symmetrical Earth, a vision of what it could be, a vision perhaps for the Valar to aim for but never achieve. I believe that with the Knowledge and foresight of the most powerful of the Valar, Melkor, he was able to infect at least one or two of the Fatherless Elves and set up a doom very early on, and sit back and wait for his plan to grow and as Tolkien say bare fruit. Perhaps his way or plan was for the Noldor to be led by Doom from their first generation. The most powerful Valar in control of the most powerful Noldo, who would possibly become part of his plan to bring down the Valar's rule from within their own land, from the inside.

Brego, earlier in this thread you suggested that maybe Melkor did something to Miriel during his captivity, then later you suggested he did something to Finwe and or Miriel before his captivity, and more recently you raise the idea of Melkor infecting some of the Unbegotten Noldor in some way.

Can you clarify please: are you changing your mind, or do you think all or some of these things occurred?

And why? I'm still not clear on why you're putting Melkor in a role that goes beyond what the texts relate with respect to his part in the Fall of the Noldor.

As far as I recall, it's not even characterized as anyone's belief (anyone inside the story) that Melkor specifically infected Finwe, Miriel, or any of the Noldorin (Tatyarin) Elves who Awoke, keeping in mind the general matter of Arda Marred, noted in a discussion among the Valar. 

No not changing my mind Galin.  These are all possibilities only, as none of us really know.

Im not saying that Miriel and or Finwe were of the first generation or Fatherless, perhaps they were , perhaps they weren't.  To clarify, I think that Melkor's Evil was possibly implanted very early on,thousands of years before the birth of Feanor.  Perhaps Miriel and Finwe carried this doom or curse with them unknowingly into Valinor from the East. Poor Feanor's doom could have been woven into the music before the creation of the Earth itself.

I truly think that Melkor was that Evil!  Nothing would surprise me.

These are all possibilities only, as none of us really know. 

But your possibilities aside, we do know the rather notable part Melkor played in the Rebellion of the Noldor (although not all the Noldor left Aman of course).

Tolkien never specifically denies the possibilities you are raising here, but then again he needn't if he never entertained them in the first place. Arda Marred (a fairly amazing infusion of power on Melkor's part) and Free Will are already part of the equation...

... and JRRT has given (to my mind) ample description of how Melkor undermined the Noldor in Aman. 

All true and literal Galin. However I believe Tolkien wanted us to realise that Melkor's reach was vast. I truly believe for reasons already stated, that Melkor had plans very very early on and his power overreached him and Iluvatar knew that in the end it would come back to haunt and or destroy him or at least his power. For me Feanor is an Elven physical manifestation of Melkor. Greedy, jealous, and proud and it was for these reasons they were both bought undone. A true fable of the potholes of greed and narcissism.

Brego, I very much agree. If I remember rightly, even in the Creation Music Melkor was at work, setting everything awry. So, even then he was planning the corruption of Feanor's heart. Just as Satan planned the corruption of Adam and Eve' s hearts.

That is my 2 cents worth. (:


Brego, I very much agree. If I remember rightly, even in the Creation Music Melkor was at work, setting everything awry. So, even then he was planning the corruption of Feanor's heart. Just as Satan planned the corruption of Adam and Eve' s hearts. 


Melkor's music was in discord of course, and he is evil in general; and his outpouring of power into the very substance of Arda, resulting in Arda Marred, was immense. But Brego has been suggesting quite specific actions within the history of Arda as it played out, actions that are not attested, nor even noted by internal characters as a belief among some (as far as I remember anyway).

And it is attested, for example, that Melkor had actually paid small heed to the Third Theme of Iluvatar. The Children of God, Elves and Men, appeared in the Third Theme:

'But Melkor spoke to them in secret of Mortal Men, seeing how the silence of the Valar might be twisted to evil. Little he knew yet concerning Men, for engrossed in his own thought in the Music he had paid small heed to the Third Theme of Iluvatar; but now the whisper went among the Elves...'

Of course Melkor knew about Elves and Men, but it seems clear enough (to me anyway), from chapter seven of the Silmarillion, that the Silmarils gnawed at Morgoth, and from this time onward Feanor became a particular target of Morgoth's hate -- but yet still his weapons here were not curses nor infections but lies, while also playing on a desire to be 'free' of greater beings and order one's own life. 

In my opinion Brego's last explanation is a bit more vague, but he had been suggesting that Melkor specifically cursed or infected (in some way) Miriel, then Finwe and or Miriel at a different point in time, then some of the Unbegotten Elves. These are actions imagined to be taking place within the history of Arda.

And even if the Music is as fate to the Elves -- meaning even if one thinks the Elves have no true free will to outwardly affect their fate -- which notion I disagree with, but at least one Tolkien scholar thinks is true, then fate still has its way of playing out. How does it play out? Is Melkor planting a curse in Miriel or Finwe? Does he need to in order to bring about Rebellion in Aman?

Again, the Silmarillion amply describes the events and motivations behind characters here. It describes what Morgoth did within the history of Arda to help bring about the fall of the Noldor. And it isn't that detailed really; it still leaves plenty of room for fan fiction even, as the Silmarillion is supposed to be a relatively brief summation of longer tales and accounts.

And for the record, I think Feanor was 'just as free willed' as any Elf...

'The Silmarils had passed away; and all one it may seem whether Feanor had said yea or nay to Yavanna; yet had he said yes at the first, before the tidings came from Formenos, it may be that his after deeds would have been other than they were. But now the Doom of the Noldor drew near.'

Silmarillion, Of The Flight of the Noldor

Galin I don't think, as you stated "Melkor was evil in general"  is correct.  He was made/created by Iluvatar of the same stuff as the other Valar or Ainur.  His evilness grew with pride and envy over millennia.  The Ainur could have existed for millions of years before their music was orchestrated.  Plenty of time for Melkor to change or evolve into an evil being.

I believe this mirrors Feanor, in some ways.  As his pride grew, as I'm sure he was constantly reminded of his greatness by the other Noldor, so did his greed.

I think there was a tipping point for both Melkor and Feaonor.  For Melkor perhaps it was simply jealousy or the feeling of shame after his period of solitude in the Void or maybe his capture and imprisonment in Mandos.  For Feanor it was either the fact that maybe he felt betrayed or at fault regarding the death of his mother or the murder of his Father.

Arath, you funny boyblushI think about your gardening a great deal and love the peaceful feeling I get.

Ah Galin and Brego, you two are so dear, your very sparring is music to my ears. I don't know what this forum would be without your brilliance and thought.

Brego wrote: Galin I don't think, as you stated "Melkor was evil in general" is correct. He was made/created by Iluvatar of the same stuff as the other Valar or Ainur. His evilness grew with pride and envy over millennia. The Ainur could have existed for millions of years before their music was orchestrated. Plenty of time for Melkor to change or evolve into an evil being.

But I didn't write Melkor was 'made' evil Brego. I've been mentioning the concept of Free Will, which allows Melkor to sing in discord.

I said Melkor was evil in general, and I meant very much 'in general', as when Tolkien writes about Morgoth with something like (letter 131) 'the power of Evil still visibly incarnate'. It was just part of a very general, and thus admittedly obvious, description of Melkor.

In short: discord yes, evil yes, Melkor is the great 'Marrer' of Arda even... but of course that doesn't mean he is specifically cursing or infecting Miriel or Finwe, or some Noldo who Awoke, in order to arrange the Fall of the Noldor.

I posted this on a different thread.

People tend to be hard on Feanor, when he was just a few that had "the curse of Aule" , the lust for creation ending in betrayal. All of whom was in relation of Aule in one way or another.

1. Aule: created the dwarves, therefore betrayed Eru and Yavanna.

2. Sauron: created the One Ring, even though his betrayal of the Valar was before he created the ring.

3. Feanor: created the Silmarils, resulting in the kinslaying.

4. Celebrimbor: created the rings of power, although didn't betrayed intentionally, the end results were the same. Was tortured and revealed the location of the rings, resulting in the death of many

5. Saruman: created machines of war, betraying Fangorn Forest by burning it down. wanting to create order upon middle earth under his rule, betrayed the white council


I made up the curse of course but I always thought it was interesting about their connections.

Feanor was a intelligent but rotten and cruel elf

Feanor as an Elf was a force of nature as his name implies. He hated Melkor most of all and loved his father above all else. Melkor murdered his father and also stole his greatest creation, the Silmarills. His quest was one of revenge not only for the theft of his jewels but the murder of his father.

His mother it seems may perhaps have been stained with Melkor's influence because this was the first time an Elf voluntarily died which lead to another unheard of thing, an Elf taking a 2nd wife. Feanor held no love for these siblings.

I do not think Feanor was evil because it does not seem to me that his intentions were evil although he was driven to evil things. He was unlike any other Elf in history. It is said his like would never reappear on Arda and that one of Melkor's greatest crimes was the marring of Feanor, "of the works of Melkor one of the most evil." [Sil, ch. 11]

There are times when people blame Feanor for the plight of the Noldor, but it is said that the darkness Galadriel saw in him, she did not see in herself and in all the other Noldor who had it too [UT, Of Galadrield and Celeborn].

Feanor's "love above all" may have been for his father once, but after the creation of the silmarils, he loved the jewels above all. His oath was not the revenge for the death of his father nor to bring Melkor to justice, but it is to recover the silmarils at all cost.

I disagree with you. Here's the passage;

"his father was dearer to him than the Light of Valinor or the peerless works of his hands; and who among sons, of Elves or of Men, have held their fathers of greatest WORTH?" [Sil, ch. 7, Flight of the Noldor]

This statement is made after Feanor learns of the death of his father at the hands of Melkor while in the Ring of Doom with Manwe. The Silmarils had long been made at this point that we are told Feanor loved his father above all else.

During his speech to the Noldor afterwords in which "Fierce and fell were his words, and filled with anger and pride" we are again brought back to his feelings for his father which motivated his words, "he was distraught with grief for the slaying of his father, and with anguish for the rape of the Silmarils." He goes on to talk about not only the loss of his Jewels but also of his father and their King for bringing him to them at this moment.

In the end, Feanor could not get back his father but he could still get the Jewels stolen from him. The death of the father and the stealing of his possessions set him off.

While his father was dearer to him, the oath was to get back the silmarils, not to get revenge. Elves are reborn, but even if the trees were restored the silmarils could not be remade. A side note is that he changed his name from Curufinwe (son of finwe) to Feanor (spirit of fire).
Feanor's words are as good as his craftsmanship. He needed to rally his people to follow him. For during his speech, he talked about the murder of his father and the theft of the silmarils. I don't take the narration as an accurate description. Since the simarillion is suppose to be a historical documentation, that was the description of the elves according to their thoughts. It's Feanor's words that shows it.

"A side note is that he changed his name from Curufinwe (son of finwe) to Feanor (spirit of fire)."

I don't agree with this. I will quote 2 passages, one from the Silmarillion and the latter from Morgoth's Ring.

"Curufinwe was his name, but by his mother he was called Feanor, Spirit of Fire" [Sil, ch. 6]

"Finwe... first named his eldest son Finwion; but later when his talent was revealed this was modified to Curufinwe. But the name of insight which his mother Miriel gave to him in the hour of his birth was Feanaro 'Spirit of Fire'; and by this name he became known to all" [MR, Laws and Customs Among the Eldar]

The first was his father name given to him by Finwe in the Essecarme. The 2nd name, or the name of insight was given to him by Miriel, which would indicate, "some dominate feature of its nature as perceived by her, or some foresight of its special fate."

Although Elves could reborn, sometimes it took Ages, and sometimes they chose not to return or were not allowed to. The Oath was a public excalamation to anyone, Vala, Elf, or Man, who would withhold the Silmarils. Of the Silmarils, "no violence could mar it or break it within the Kingdom of Arda." [Sil, ch. 7] The oath he and his sons took was not an oath of revenge, but the oath was not the only reason he took his course.

Firstly, let it be known that I was only joking when I said he changed his name, but if he didn't, why did Tolkien refer to him only as Feanor? Perhaps it has a bit more ring to it.

Without the oath the history of the Noldor would probably have been dramatically different. If not for the oath, Feanor would not have been driven to secure the fastest possible means of transport, and would not have committed the first kinslaying. Perhaps they would have been persuaded to stay in Valinor, and they certainly would not have been shut out of Valinor. Their cries would not fall on deaf ears, and ships requesting aid from Valinor would have come sooner. So in my opinion, the oath was one of the primary reasons he and his sons took the course they did.

Also according to Morgoth's Ring it seems that Curufinwe took Feanáro as his Chosen-name too, in honour of Miriel 'whom he never saw'. So it appears that both his Mother-name and Chosen-name was Feanáro...

... that said, a later text that includes an account of naming customs [if briefer] makes no mention of the custom [possibly only a Noldorin custom in any case] of this type of Chosen-name, and in this text Feanor did see Miriel alive.

As Feanor grew more immersed in his works and Pride, His hate of his wise brothers Fingolfin, and Finarfin. He burned the ships out of spite at Losgar. Fingolin's son Fingon forgived that great wrong by rescuing Maedhros from terrible and despairing imprisonment. Feanor was most likely the longest to stay in the Halls of Mandos.(maybe besides Saeros!) So all in all, Feanor distrusted His step mother Indis because of Jealousy and pride.

But were they implanted in him by Morgoth, to sunder forever the Eldar, who he knew would surely lose if they did not unite?

Firstly, let it be known that I was only joking when I said he changed his name, but if he didn't, why did Tolkien refer to him only as Feanor? Perhaps it has a bit more ring to it.

It seems that Tolkien kept changing his mind here. In the 'Etymologies period' for instance [generally speaking, before the writing of The Lord of the Rings was finished] Tolkien imagined Feanor as a Noldorin name meaning 'Radiant sun'...

... but JRRT not only changed the meaning of Feanor, ultimately he drastically changed the history of his languages, and in the new scenario we do not have Noldorin but Sindarin, and the Noldor only learned Sindarin sometime after they returned to Middle-earth...

... and as 'Feanor' was slain relatively quickly upon his return to Middle-earth, he was likely called Feanáro at the time of his death. But later when the histories were written, certain Quenya names had been 'Sindarized' or were altered due to Sindarin.

Tolkien seems to have liked Feanor, or in any case he had been used to this form for many years. He ultimately published it, and found a way to explain it within the new concept...

'Feanor is the form nearly always used in histories and legends, but is as it stands only half Sindarized: the genuine Sindarin form was Faenor, the form Feanor (...) probably arose through scribal confusion. especially in documents written in Quenya, in which ea was frequent but ae did not normally occur.'

JRRT, The Shibboleth of Feanor

In an earlier text published in Morgoth's Ring, Feanor was said to be the form the name Feanáro took in Beleriand, with Feanor being more often used. Tolkien revised this somewhat and added Sindarin Faenor to the mix, calling Feanor a 'blend' of Quenya and Sindarin; and then we have the idea as noted above. 

So in short: the formerly 'Noldorin' name Feanor had to be explained within the new Quenya and Sindarin scenario of The Lord of the Rings [and in relatively later texts], and so Tolkien invented the notion that it was half Sindarized and probably arose through scribal confusion.