A verb appearing as G. gweltha- “squeeze, press” in the Gnomish Lexicon of the 1910s, apparently based on G. gwel- “boil, bubble” (GL/44-45), perhaps originally meaning “*make bubble”. This verb was the basis for G. mirwelthin “vintage”, more literally “*wine-squeezing” (GL/45, 57).

Neo-Sindarin: Since I retain ᴺS. gwel- “to boil, bubble” for purposes of Neo-Sindarin, I would retain ᴺS. gweltha- “to squeeze, press” as well. In spelling this word would have lth, but in pronunciation it would be long voiceless [l̥] as with Welsh “ll”.