This root first appeared in The Etymologies of the 1930s as ᴹ√NIS “woman”, an extension of ᴹ√NĪ “female” (Ety/NIS). It also had a strengthened form ᴹ√NDIS, unglossed but apparently meaning “bride” based on its derivatives ᴹQ. indis/N. dîs of that meaning (Ety/NDIS). Unstrengthened ᴹ√NIS seems to have survived only in Quenya as the basis for ᴹQ. nis (niss-) “woman”, but this word was also blended with ✱ndis-sē to produce a longer form nisse of the same meaning.
In Tolkien’s later writings, both short Q. nís and longer nissë appeared as words for “woman” (MR/213; VT47/33) and Q. indis reappeared as well, though glossed “wife” (UT/8). As primitive forms, both unstrengthened √nis (VT47/33) and strengthened ✶ndī̆s “woman” also appeared in later writings, the latter given as the feminine equivalent of ✶[[p|n[d]ēr]] “man” (PE19/102).
Tolkien used a similar set of Elvish roots for “youth” and “freshness” for many years. The earliest of these was primitive guı̯u̯ or gu̯iu̯ [ᴱ√GWIWI] in the Gnomish Lexicon of the 1910s with derivatives like G. gui “just, just now, only just, already”, G. guin “recent, fresh”, and G. gwioth “youth” (GL/42). This root reappeared as ᴹ√WIR “new, fresh, young” in The Etymologies of the 1930s with variants ᴹ√WĪ and ᴹ√WIN and derivatives ᴹQ. vírie “youth” and ᴹQ. virya “fresh” (EtyAC/WIR). The ᴹ√WIN variant had derivatives ᴹQ. vinya/N. gwîn “young”. Tolkien considered, but rejected, deriving these from strengthened ᴹ√GWIN instead, producing (also rejected) ᴹQ. winya/N. bîn (EtyAC/GWIN).
Q. vinya appeared in quite a few later names with the gloss “young” or “new”, but the Sindarin form became S. gwain as in S. Narwain “January, ✱(lit.) New Fire” (LotR/1110) and S. Iarwain “Old-young” (LotR/1114; RC/128). In Definitive Linguistic Notes (DLN) from 1959, both were given as derivatives of √WIN “young” along with Q. víne/S. gwîn “youth”, though the Sindarin word for “young” was given as (archaic?) gwein (PE17/191). Also related are various words for “baby” from 1968 notes such Q. †wine/S. gwinig “little-one, baby” (VT48/6). In these notes primitive wini was glossed “little” but this was deleted (VT47/26), making it likely that the earlier senses “young, new” were restored for √WIN.
As for the 1930s root ᴹ√WIR, it might have survived as an element in the month names Q. Víressë/S. Gwirith “April” (LotR/1110), perhaps meaning “✱freshness”.