A less common Quenya word for “daughter”, an analog of Q. yondo “son”.
Conceptual Development: In The Etymologies of the 1930s Tolkien had ᴹQ. yelde “daughter” under the root ᴹ√YEL of the same meaning, but the meaning of the root was first changed to “friend”, and then the root was then deleted (Ety/YEL). Meanwhile, under the root ᴹ√YŌ or YON, Tolkien introduced a feminine variant ᴹQ. yende “daughter” along with (suffixal?) yen, derived from primitive ᴹ√yēn or yend (Ety/YŌ). Previously this yende/yendi form was a feminine agent, but Tolkien rejected that meaning (EtyAC/ƷAN).
In between yelde >> yende for “daughter” in The Etymologies, Tolkien considered using the form ᴹQ. selde, and in later writings this seems to be his preferred Quenya word for “daughter”. However, yeldë “daughter” was mentioned again briefly in rough notes from around 1959 (PE17/190), and -iel remained Tolkien’s preferred suffix for “daughter of”.
Neo-Quenya: For purposes of Neo-Quenya, I recommend seldë as the more common word for “daughter”, but assume yeldë also exists as variant due to the influence of yondo “son”; see the entries on seldë and the root √YE(L) for further discussion.
This seems to be the word that Tolkien favored for “daughter” in his later writings (PE17/170; VT47/10; PE19/73), though it had competition from other forms like Q. yeldë.
Conceptual Development: The earliest word resembling this form was ᴱQ. sui “daughter” in the Qenya Lexicon of the 1910s under the early root ᴱ√SUẈU (QL/87), a word also mentioned in the Poetic and Mythological Words of Eldarissa (PME/87). This became ᴱQ. silde “daughter” in Early Qenya Word-lists of the 1920s (PE16/135).
In The Etymologies of the 1930s, Tolkien experimented with several different forms. He had ᴹQ. yelde “daughter” under the root ᴹ√YEL, but this entry was deleted (Ety/YEL). Tolkien also had a root ᴹ√SEL(D) “daughter” with a derivative ᴹQ. selde, but the meaning of this root was changed to “child”, and masculine and neuter forms ᴹQ. seldo and ᴹQ. selda were added to the entry (Ety/SEL-D). Finally, under the entry for ᴹ√YŌ or YON “son”, Tolkien added a primitive feminine variant ᴹ✶yēn or yend “daughter”, producing ᴹQ. yende and (suffixal?) yen (Ety/YŌ).
These vacillations continued in later writings, where at one point Tolkien wrote “Q[uenya] Wanted: Son, Daughter” (PE17/170). In Notes on Names (NN) from 1957 Tolkien wrote Q. sel-de for “daughter”, but above it he wrote a variant form anel. In rough notes from around 1959 Tolkien explored a large number of masculine and feminine suffixes, and on the page he had yeldë “daughter”, though at the end of the sentence he wrote “also yen” (PE17/190). In notes on Eldarin Hands, Fingers and Numerals from the late 1960s, Tolkien wrote selyë as a diminutive/affectionate word for “daughter”, with seltil as a play name for the fourth finger representing a daughter (VT47/10, 27).
Also of note is Tolkien’s Quenya name for S. Tinúviel “Daughter of Twilight”, which he generally represented as something like Q. Tindómerel < ✶Tindōmiselde. Tolkien was fairly consistent in this Quenya form starting in the 1930s (Ety/SEL-D; PE19/33), with examples in the 1950s (PE19/73) and 1960s (VT47/37) as well. Indeed, in a couple cases he used this name to illustrate how medial s generally became z and eventually r in Quenya (PE19/33, 73), so it seems that for this name Tolkien consistently imagined the primitive form for “daughter” as ✶selde.
Neo-Quenya: I’d assume selde is the main word for “daughter” for purposes of Neo-Quenya, but I’d assume a variant form yeldë, especially since -iel was the most common suffix for “daughter of”. This variant probably arose very early under the influence of √YON “son”.