spirit of fire (pure S of half S - half Q Fëanor); faer (“spirit”) + naur (“fire”) S form of Q Fëanáro.
Sindarin
faen
noun. vapour; [disembodied] spirit
faen
adjective. radiant, white
Faenor
noun. Faenor
faenor
masculine name. Spirit of Fire
fain
noun/adjective. white
fain
noun/adjective. cloud
faen
radiant
faen (white). No distinct pl. form.
faen
white
(radiant). No distinct pl. form.
faen
radiant
(white). No distinct pl. form.
fain
white
; no distinct pl. form.
fëanor
masculine name. Spirit of Fire
Greatest of the Noldor and crafter of the Silmarils (LotR/657). His Sindarin name is a partial adaptation of his mother-name Q. Fëanáro “Spirit of Fire”, as opposed to a pure Sindarin translation, which would have been Faenor (MR/217, PM/343). As such, it is a combination of Q. fëa “spirit” and the suffixal form -nor of S. naur “fire”.
Conceptual Development: The earliest mention of this name is in the Gnomish Lexicon from the 1910s, where ᴱQ. Feanor is explicitly marked Qenya, with a cognate G. Fionor (< Fionaur) “Goblet Smith” in Gnomish (GL/35). The language of the name Feanor in earliest Lost Tales is not specified, but it is probable that Tolkien re-imagined the name as Gnomish at an early stage, since both Feanor and his father Bruithwir were of the Noldoli (LT1/128, 145).
In the Silmarillion drafts and The Etymologies from the 1930s, the name N. Feanor is explicitly marked as Noldorin, with a Qenya equivalent ᴹQ. Feanáro, both developed from primitive ᴹ✶Phayanāro “Radiant Sun” (Ety/PHAY). However, the phonetic developments leading from ᴹ✶Phaya- to N. Fea- are obscure, and the combination [ea] does not occur in any other Noldorin word. This is likely the reason Tolkien developed the mix-language derivation discussed above, which appears in notes associated with the Silmarillion revisions from the 1950s-60s.
glân
white
1) glân (clear), lenited lân, pl. glain. (UT:390, VT45:13). Note: a homophone means ”hem, border”. 2) nimp (nim-) (pale); no distinct pl. form. 3) faen (radiant). No distinct pl. form. 4) fain; no distinct pl. form.
glân
adjective. white, [bright shining] white; [N.] clear; [G.] pure, †bright; [ᴱN.] clean
nim
white
_adj. _white. >> Nimbrethil
nim
white
nim
adjective. white
silivren
adjective. (white) glittering
uilos
noun/adjective. always white, ever white as snow
uilos
noun/adjective. a small white everlasting flower also called simbelmynë or "evermind"
gloss
white as snow, dazzling white
(in compounds -los), lenited ’loss; pl. glyss.
glân
white
(clear), lenited ’lân, pl. glain. (UT:390, VT45:13). Note: a homophone means ”hem, border”.
nimp
white
(nim-) (pale); no distinct pl. form.
silivren
glittering white
(lenited hilivren; pl. *silivrin**). *Verb
A word for “vapour” in some 1957 notes derived from √PHAY “spirit”, also referring to disembodied spirits as the equivalent of Q. fairë for “spirit” (NM/237).
Neo-Sindarin: For purposes of Neo-Sindarin, I’d use better-known S. faer for a disembodied spirit (MR/349), a more direct cognate of Q. fairë, but I see no reason why faen can’t be used for vapour.