rumen.

From Proto-Italic *roug(s)mən ~ *rug(s)mən, of somewhat disputed origin. Probably from the root of *rūgō + -men, attested in ērūgō, rūctō (“to belch”) and rugiō (“to roar, rumble, bray”), from Proto-Indo-European *h₁rewg-, *h₁rewǵ- (“to belch”). Cognate with Ancient Greek ἐρεύγομαι (ereúgomai, “to spew out, discharge, belch, bellow”), Old Armenian ործամ (orcam, “to vomit, be nauseated”), Proto-Germanic *reukaną (“to smoke, emit vapor”) (modern English reek). Alternatively from Proto-Indo-European *sréwmn̥, from the root *srew- (“to flow”). See also Rōma and flūmen, which are sometimes hypothesized as from the same source. A third possibility is a relationship with Etruscan 𐌓𐌖𐌌 (rum, “teat”). If not coincidental, it may be equally likely that the Etruscan word was borrowed from Latin.