A verb in the Gnomish Lexicon of the 1910s glossed “smoulder” (GL/36). It was marked with a “✱” which Tolkien used to begin a group of words based on a common root, probably ✱ᴱ√FUKU in this case.
Quenya
yol-
verb. to smoulder
Beware, older languages below! The languages below were invented during Tolkien's earlier period and should be used with caution. Remember to never, ever mix words from different languages!
Qenya
yul-
verb. to smoulder
Gnomish
fug-
verb. to smoulder
In The Etymologies of the 1930s, the verb ᴹQ. yul- “smoulder” was mentioned in passing in a deleted entry for the root ᴹ√GUL (Ety/GUL). Since the root ᴹ√YUL “smoulder” remained undeleted in The Etymologies, perhaps this verb also remained valid in the 1930s (Ety/YUL). However, the later meaning of the verb Q. yul- was “drink” from the root √YUL of the same meaning (PE17/63).
Neo-Quenya: For purposes of Neo-Eldarin, I would adapt the root ᴹ√YUL “smoulder” as the Neo-Root ᴺ√YOL, and hence would adapt this 1930s verb as ᴺQ. yol- “smoulder” to sidestep the conflict with Q. yul- “drink”; see the entry on ᴺ√YOL/YUL for further discussion.