A word appearing as G. mirwelthin “vintage” in the Gnomish Lexicon of the 1910s, a combination of G. mîr “wine” and an (adjectival?) form of the verb G. gweltha- “squeeze, press” (GL/45, 57).

Neo-Sindarin: I would adapt this word slightly as ᴺS. mirwelthen “vintage, *(lit.) wine pressing” using a more ordinary Sindarin adjective suffix -en, and would assume the initial element is ᴺS. miru “wine” as seen in miruvor.