√USUK root. “dusk, evening”
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 Qenderinwa 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”.
References ✧ PE18/100; PE21/71
ᴹ√USUK root. “*reek, smoke; dusk”
References ✧ Ety/USUK; PE18/50