√UÑG “spider”
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/491, 767).
√UR “heat, be hot”
This root was connected to “heat” for most of Tolkien’s life. It first appeared as unglossed ᴱ√URU in the Qenya Lexicon of the 1910s, with derivatives like ᴱQ. úrin “(blazing) hot”, ᴱQ. uru “fire”, G. urin “hot, very hot”, and G. urna- “blaze, burn” (QL/98; GL/75). In this early period it was blended with the root ᴱ√UŘU with variant ᴱ√USU which had derivatives like ᴱQ. urna “oven” and ᴱQ. usta- “burn” (QL/98). This second root had derivatives in the contemporaneous Gnomish Lexicon such as G. gund “boil, pus” and gusta- “burn, destroy” from primitive *gudh (GL/42), indicating the actual root form was *ᴱ√ƷUÐU.
*ᴱ√ƷUÐU seems to have been abandoned in Tolkien‘s later writings, but ᴹ√UR “be hot” appeared in The Etymologies of the 1930s with derivatives like ᴹQ. úr/N. ûr “fire” and ᴹQ. urya- “blaze” (Ety/UR). This entry was deleted and replaced by ᴹ√UR “wide, large, great”. This was likely a transient change, however, as ᴹQ. Úrin as a name of the Sun remained in contemporaneous Silmarillion drafts (LR/240). Indeed primitive √UR appeared several times in later writings as the basis for words for “sunlight”, “fire” and “heat” (PE17/120, 148; PE21/71; PE22/160).
ᴱ√USU “get out, escape”
The root ᴱ√USU⁽¹⁾ appeared in the Qenya Lexicon of the 1910s with the gloss “get out, escape” and derivatives like ᴱQ. usu- “he escapes” and ᴱQ. uswe “issue, outlet, escape” (QL/98). In the contemporaneous Gnomish Lexicon it had derivatives like G. us(ta)- “leave, depart” and G. uthwen “way out, exit; escape” (GL/75), the latter hinting that the root form may have been a blending with *ᴱ√UÞU. I think it is worth positing a Neo-Eldarin root ᴺ√UTH to salvage these early words for “escape”.
√USUK “️dusk, evening; [ᴹ√] *reek, smoke”
This root has a long history in Tolkien’s Elvish languages, but its meaning shifted over time. The earliest iteration of this root was unglossed ᴱ√ṢQṢ in the Qenya Lexicon of the 1910s (marked by Tolkien with a “?”) with derivatives like ᴱQ. usqe “fog” and G. usc “fog, mist” (QL/98; GL/75). In The Etymologies of the 1930s Tolkien had unglossed ᴹ√USUK with derivatives like ᴹQ. usqe “reek” and N. osp “smoke” (Ety/USUK). In both the first and second version of Tengwesta Quenderinwa from the 1930s (TQ1) and around 1950 (TQ2) Tolkien had √USUK > Q. usquë “dusk” (PE18/50, 100). In Common Eldarin: Noun Structure Tolkien had primitive ✶usuk “dusk, evening”, again with derivative Q. usquë (PE21/71). For purposes of Neo-Eldarin, I would stick with the 1930s sense “*smoke, reek” for this root, as Elvish languages already have plenty of roots for “dusk”.
√UTHU “bad; unsuitable; improper, useless, wrong; [wrong] with a bad sense”
This root appeared in a page of roots from Definitive Linguistic Notes (DLN) from 1959 with the gloss “unsuitable, bad, improper, useless, wrong” (PE17/172). This page was rejected, but the root √UTHU appeared again later in DLN as the basis for prefixes meaning wrong “with a general bad sense”: Q. us- and S. oth- as in S. othgarn “misdeed” and Q. uskare > Q. uxarë of the same meaning (PE17/151).
ᴹ√UY “*long trailing plant”
An unglossed root in The Etymologies of the 1930s with derivatives like ᴹQ. uile “long trailing plant, especially seaweed” and N. uil “seaweed” (Ety/UY). In this document it also was the basis of the name of the Vali ᴹQ. Uinen, but in later writings Tolkien said this name was not Elvish, but was adapted from Valarin (WJ/404). This may mean the root ᴹ√UY was abandoned, but I would retain it for purposes of Neo-Eldarin to preserve these 1930s words for “seaweed”.