This is apparently an adjectival form of aew “(small) bird” appearing in the name Linaewen “Lake of Birds” (S/119, SA/lin¹, UT/401), formed using the adjective suffix -en.
Sindarin
aew
noun. (small) bird
aew
noun. (small) bird
aewen
adjective. of birds
aewen
adjective. of birds
maew
noun. gull
A noun for “gull” first appearing as N. maew in The Etymologies of the 1930s derived from the root ᴹ√MIW “whine” (Ety/MIW). It appeared in later notes as an archaic genitive plural maewion in the phrase S. †glim maewion “(the) voices of gulls” (PE17/97). Its class plural mewrim seems to have appeared in S. Ras Mewrim “✱Cape of the Gulls”, an alternate name for S. Bar-in-Mŷl “Home of the Gulls” (WJ/190). If so, the vowel e would be the result of the sound change whereby ae sometimes became e in polysyllables.
aew
aew
aew
small bird
aew. No distinct pl. form.
aew
bird
(small bird) 1) aew. No distinct pl. form. 2) fileg, pl. filig; the form filigod appears as an alternative singular. or
aew
small bird
. No distinct pl. form.
aew
bird
. No distinct pl. form.
aewen
of birds
pl. aewin.
aewen
of birds
aewen, pl. aewin.
maew
gull
1) maew (i vaew), no distinct pl. except with article (i maew), coll. pl. maewrim; 2) gwael (i **wael), no distinct pl. form except with article (in gwael), 3) mŷl (i vŷl, construct myl), no distinct pl. form except with article (i mŷl**).
maew
gull
(i vaew), no distinct pl. except with article (i maew), coll. pl. maewrim
mŷl
noun. gull
A word for “gull” in the name S. Bar-in-Mŷl “Home of the Gulls” (WJ/379); its singular and plural forms would be the same. It might be derived from ✱miulē < ᴹ√MIW “whine”, the basis for other “gull” words, since iu became ȳ in Sindarin. I’d recommend using the better attested S. maew “gull” for purposes of Neo-Sindarin.
cidinn
adjective. small
_ adj. _small. Q. cinta.
cinnog
adjective. small
_ adj. _small. Q. cinta.
gwael
noun. gull
mŷl
noun. gull
niben
adjective. small, petty
niben
adjective. little finger (Elvish play-name used by and taught to children)
nimp
adjective. small and frail
cuen
small gull
(i guen, o chuen) (petrel), pl. ?cuin (?i chuin) (VT45:24)
emlinn
yellowhammer
(= "yellow singer"); no distinct pl. form. Also emelin, no distinct pl. form; coll. pl. emelinnath. Adj.
fileg
bird
pl. filig; the form filigod appears as an alternative singular.
glâd
small forest
(i ’lâd, construct glad) (wood), pl. glaid (in glaid).
gwael
gull
(i ’wael), no distinct pl. form except with article (in gwael)
hûb
small landlocked bay
(i chûb, o chûb, construct hub) (harbour, haven), pl. huib (i chuib).
m
gull
ŷl (i vŷl, construct myl), no distinct pl. form except with article (i mŷl).
mîw
small
1) mîw (tiny, frail), lenited vîw, no distinct pl. form, 2) niben (petty), pl. nibin. Also used as a name for the the little finger. (VT48:6) 3) SMALL (and frail) nimp, no distinct pl. form (VT48:18)
mîw
small
(tiny, frail), lenited vîw, no distinct pl. form
niben
small
(petty), pl. nibin. Also used as a name for the the little finger. (VT48:6)
nimp
small
no distinct pl. form (VT48:18)
paen
small gull
(i baen, o phaen) (petrel), no distinct pl. form except with article (i phaen). Suggested Sindarin form of ”Noldorin” poen, VT45:24.
pêg
small spot
(i** bêg, construct peg) (dot), pl. pîg (i** phîg)
tinu
small star
(i** dinu, o thinu; also -din at the end of compounds) (spark), analogical pl. tiny (i** thiny). Archaic tinw, so the coll. pl. is likely tinwath.
A noun meaning “(small) bird” (SA/lin¹, Ety/AIWĒ), appearing in the name Linaewen “Lake of Birds” (S/119, UT/401). It was derived from primitive ᴹ✶aiwē like its Quenta cognate aiwë (Ety/AIWĒ), with the primitive diphthong ai becoming the ae in Sindarin.
Conceptual Development: In the Gnomish Lexicon from the 1910s, G. aigli “bird” was given as a derivative of the root ᴱ√aı̯, though in this early iteration Tolkien said it especially applied to larger instead of smaller birds (GL/17). In Early Noldorin notes from the 1920s, it became ᴱN. aiw “bird” (PE13/136, 158). In The Etymologies from the 1930s, the form became N. aew “(small) bird” (Ety/AIWĒ), and this is the source of the derivation given above.