The name that Beren gave to Lúthien, translated “Nightingale”, more literally “Daughter of Twilight” (S/165), a derivation of the primitive form ✶Tindōmiselde (PE19/73). It is essentially a combination of tinnu “twilight” and the suffix -iel, except that the archaic final -v lost in tinnu was preserved in the compound.
Conceptual Development: This name first appeared as G. Tynwfiel in the earliest Lost Tales, probably a Welsh-like spelling of the name, but this was revised to Tinúviel (LT2/41), the form Tolkien more or less retained thereafter. The translation “Nightingale” for ᴱN. Tinúviel emerged in the Lays of Beleriand from the 1920s (LB/153). In The Etymologies from the 1930s, N. Tinúviel had the same derivation as given above (Ety/SEL-D, TIN).