From a passage inadvertently omitted from the published version of The Silmarillion (LR/301), this name is a combination of eithel “fountain” and nínui, apparently an adjective meaning “✱tearful”.
Noldorin
tinúviel
feminine name. Nightingale, (lit.) Daughter of Twilight
Tinnúviel
noun. nightingale
eithel nínui
place name. Fountain of Tinúviel
duilin
noun. nightingale
dúlin
noun. nightingale
dúlin(n)
noun. nightingale
dúlind
noun. nightingale
dúlinn
noun. nightingale
merilin
noun. nightingale
merilin(n)
noun. nightingale
mœrilind
noun. nightingale
nightingale