ailin ("g.sg. ailinen", in Tolkien's later Quenya dat.sg.) "pool, lake" (AY, LIN1, LT2:339). Fem. name Ailinel (likely Ailinell-), perhaps ailin + the feminine ending -el (as in aranel "princess"), hence "Lake-woman" or similar (UT:210).
Quenya
ailinel
feminine name. Ailinel
Elements
Word Gloss ailin “a large lake, (large) lake, [ᴹQ.] pool” -iel “-daughter; feminine suffix”
ailin
g.sg. ailinen
ailinel
Ailinel
Ailinel's name appears to incorporate one of the Quenya words for "lake", ailin, and the feminine suffix -el.
The second child of Tar-Meneldur (UT/173). Her name seems to be a compound of ailin “lake” with the feminine suffix -(i)el.