A word for “bride” in The Etymologies of the 1930s derived from primitive ᴹ✶ndīse under the root ᴹ√NDIS (Ety/NDIS). Ordinarily the s in this word would have been lost, but it was influenced by N. †dess “young woman” < ON. ndissa from the same root (EtyAC/NDIS). Dîs “bride” in turn influenced the form of N. †dî “woman”, originally ON. nī < ᴹ√NĪ (Ety/DER, NĪ¹; EtyAC/NDIS).
Neo-Sindarin: While I think this word is perfectly serviceable, for purposes of Neo-Sindarin it may be better to use the longer and more distinctive word dineth for bride.
A feminine agental suffix appearing in The Etymologies of the 1930s as a suffix in N. meldis “friend (f.)”, the feminine equivalent of N. meldir which had the masculine agental suffix dîr (Ety/MEL).
Conceptual Development: In the Gnomish Lexicon of the 1910s the suffix G. -(n)ir seems to be a feminine agent, probably based on (archaic) G. †nîr “woman”. For example: G. bridh(n)ir “queen” vs. G. bridhon “king” (GL/24) or G. gwar(e)dhir “f. companion” vs. G. gwar(e)dhon “m. companion” (GL/44). Sometimes -ir seems to be gender-neutral, however, as with G. faithir “savior” (GL/33) and G. hilmir “heir (m. or f.)” (GL/49). There are remnants of this feminine -ir suffix in The Etymologies, where in the first iteration of the entry for the root ᴹ√MEL Tolkien had meldir “friend (f.)” (EtyAC/MEL) before deciding meldir was masculine.