ᴺS. [N.] ^dovn adj. “gloomy” (Category: Dark, Murky)
A word given as N. dofn “gloomy” in The Etymologies of the 1930s with variant dufui, both derivatives from the root ᴹ√DUB “loom, hang over oppressively (of clouds)” (Ety/DUB; EtyAC/DUB). The form dofn is the cognate of ᴹQ. lumna “lying heavy, oppressive” and shows a-affection, whereas dufui seems to be a Noldorin invention using the adjective suffix -ui, and thus preserves its primitive stem-vowel u.
Neo-Sindarin: For Neo-Sindarin, I’d write both forms as ᴺS. dovn and duvui to better reflect their pronunciation.
References ✧ Ety/DUB; EtyAC/DUB
|ᴹ√DUB > dofn||[dubna] > [dumna] > [domna] > [domn] > [dovn]||✧ Ety/DUB|
|ᴹ√DUB > dufui||[dubui] > [duvui]||✧ EtyAC/DUB|