This root and ones like it were tied to spider words for much of Tolkien’s life, most notably in the name S. Ungoliant and its precursors. The earliest iteration of this root was unglossed ᴱ√GUŊU in the Qenya Lexicon of the 1910s with derivatives like ᴱQ. ungwe/G. gung “spider” (QL/98); Tolkien marked the root with a “?” and given that the Qenya forms had no initial consonant, the actual root may have been ✱ᴱ√ƷUŊU. In The Lost Tales of the 1910s, Tolkien changed G. Gungliont to G. Ungoliont (LT1/156), and in the contemporaneous Gnomish Lexicon the word for “spider” was G. ungwi (GL/75), so it seems Tolkien revised {✱ᴱ√ƷUŊU >>} ✱ᴱ√UŊU.
In The Etymologies of the 1930s, unglossed ᴹ√UÑG had derivatives like ᴹQ. ungwe “gloom” and ᴹQ. ungo “cloud, dark shadow” (Ety/UÑG), and it was the second element ᴹQ. liante in ᴹQ. Ungoliante that meant “spider” (Ety/SLIG). However, in notes from 1969 Tolkien gave ✱ungu- as the basis for “spider” words (PE22/160), as reflected in Q. ungwë “spider’s web” (LotR/1122) and S. ungol “spider” in his later writings (Let/180; RC/490, 767).
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”.