A feminine suffix common in Quenya names, in one place given as a feminine patronymic (PE17/170), though there are no attested Quenya names in which it was used that way.
Conceptual Development: In The Etymologies of the 1930s, ᴹQ. ien was given as a (suffixal?) variant of ᴹQ. yen(de) “daughter” (Ety/YŌ; EtyAC/YŌ), but again there are no actual names from this period using the suffix in that way.
The most common Quenya suffix for “daughter of” such as in Elerondiel “✱Daughter of Elrond” (PE17/56) or Uinéniel “Daughter of Uinen” (UT/182).
Conceptual Development: The earliest hint of this suffix was ᴱQ. -il mentioned by Tolkien in the Qenya Lexicon of the 1910s as the equivalent of feminine patronymic ᴱQ. -wen (QL/103), but its only use in this period was in the masculine name ᴱQ. Indorildo, a variant of ᴱQ. Indorion and hence probably meaning “son of” (LT2/217). In The Etymologies of the 1930s Tolkien mentioned ᴹQ. -iel as a feminine patronymic under the root ᴹ√YEL “daughter” (Ety/YEL¹), but this root was rejected and in that document Tolkien seems to have replaced it with ᴹQ. -ien (EtyAC/YŌ).
In later writings Tolkien considered a bewildering variety of suffixes for the feminine patronymic, including -iel(d), -well, -wend and -ien (PE17/170, 190). In practice, though, only -iel appeared in actual names for “daughter of” (see above), perhaps because it is was the cleanest equivalent of the well-established masculine patronymic -ion “son of”.