Tindómieldaughter of twilight
Tindómiel, fem. name (UT:210), probably *"daughter of twilight" (tindómë + -iel) and thus the equivalent of Sindarin Tinúviel. Compare tindómerel.
tindómereldaughter of twilight
tindómerel (also capitalized Tindómerel) fem. name "daughter of twilight", a kenning (poetic name) of the nightingale; = Sindarin Tinúviel. (TIN, SEL-D, SA:tin; "Tindómrl" in mirrored Tengwar in VT47:37 would seem to be an incomplete annotation of the same word). The form Tindómiel (UT:210) could well be an alternative Quenya equivalent of Tinúviel, and it is possibly to be preferred because the status of the ending -rel "daughter" is uncertain (it was to represent older -zel, -sel corresponding to the independent word seldë, but Tolkien changed the meaning of this word from "daughter" to "child", and since the word for "child" appears as hína in later texts, it may be that seldë and the corresponding ending -rel were dropped altogether).
tindómerelfeminine name. Daughter of Twilight
The Quenya name of Tinúviel (SA/tin, PE19/00 73). Since she was a Sindarin elf, this name is largely theoretical, as a development from the same primitive form: ✶Tindōmiselde. This name is a compound of tindómë and a suffixal form -rel of seldë “daughter”. In a couple places, Tolkien used this name to illustrated the development of primitive intervocalic ✶[s] into Quenya [r] (PE19/00 33, 73).
Conceptual Development: The earliest “Qenya” name for Tinúviel was ᴹQ. Tinúviel in linguistic notes from the early 1930s; it was declined in various noun cases, and was clearly intended to be a purely Qenya name rather than an adaptation of the Noldorin Tinúviel (PE21/35). The name ᴹQ. Tindómerel appeared in the Etymologies from the mid-1930s, where it already had the derivation described above (Ety/SEL-D, TIN). In some notes on Quenya phonology from the 1930s, this name appeared as Tindómirel with a medial i (PE19/00 33), but in a revision of those notes from the 1950s it was reverted back to Tindómerel (PE19/00 73). It appeared as tindómrl (Tindómrl) in some examples of left-handed tengwar writing from the 1960s (VT47/37); Tolkien probably neglected to add the vowel diacritics in this case.