Middle Primitive Elvish
yul
root. smoulder
Derivatives
sug
root. drink
sok
root. drink
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!
A root in The Etymologies of the 1930s glossed “smoulder” with derivatives like ᴹQ. yúla/N. iûl “ember(s)” and ᴹQ. yulma/N. iolf “brand” (Ety/YUL). In all likelihood it was supplanted by the later root √YUL “drink”.
Neo-Eldarin: Despite it’s probable replacement by √YUL “drink”, I’d still recommend using some derivatives of ᴹ√YUL “smoulder” for purposes of Neo-Eldarin. Noldorin forms like iolf and iûl are not viable as derivatives in Sindarin, since initial yu- became the (vowel) y, for example: ýneg < ✶yūneke (VT47/41). But the Noldorin forms could be adapted into (Neo) Sindarin if they were derived from a Neo-Root ᴺ√YOL. Quenya forms could likewise be transferred to this root, or retained unmodified if we assume an occasional √YOL/YUL variation, similar to vowel variations like √SOK/SUK (PE18/45, 94). Assuming the existence of such a ᴺ√YOL/YUL Neo-Root would allow many of these 1930s forms to be salvaged without directly conflicting with √YUL “drink”.