An Elvish noun Tolkien used for much of his life but with shifting meanings: 1910s “fog” >> 1930s “reek” (= smoke) >> 1940s-1950s “dusk”. This word first appeared as ᴱQ. usqe “fog” in the Qenya Lexicon of the 1910s as a derivative of the early root ᴱ√ṢQṢ (QL/98), also mentioned in the contemporaneous Gnomish Lexicon as a cognate of G. usc “fog, mist” (GL/75). In The Etymologies of the 1930s it was ᴹQ. usqe “reek”, cognate of N. osp “smoke”, both derived from primitive ᴹ✶us(u)k-wē under the root ᴹ√USUK (Ety/USUK).
However, in both the first and second versions of the Tengwesta Qenderinwa from the 1930s (TQ1: PE18/50) and 1950s (TQ2: PE18/100) usque had the same basic derivation but was glossed “dusk”. The word usqe “dusk, twilight” appeared in documents on The Feanorian Alphabet from the 1940s (PE22/51) and in Common Eldarin: Noun Structure from the early 1950s uskwe was given as the Q. derivative of √USUK “dusk, evening”. In the Outline of Phonology (OP2) from the early 1950s usque was glossed “dim light, especially of early dawn” (PE19/84).
Neo-Quenya: Although it is fairly clear Tolkien changed the meaning of this word from “reek” to “dusk”, many Neo-Quenya writers continue to use usque with its meaning from The Etymologies of the 1930s, since we have plenty of other “dusk” words but few words for “smoke”. The 1930s sense “reek” is a noun, and hence probably tied to Old English sense of the word, which was “smoke” before it had the later sense “stench”, so I’d use usque primarily as “✱smoke” and only secondarily as “reek” = “stench”.
dusk