ferment (v.) Look up ferment at Dictionary.com
late 14c., from Old French fermenter (13c.) and directly from Latin fermentare "to leaven, ferment," from fermentum "substance causing fermentation, leaven," from root of fervere "to boil, seethe" (see brew). Figurative use from 1650s. Related: Fermented; fermenting.
ferment (n.) Look up ferment at Dictionary.com
early 15c., from Middle French ferment, from Latin fermentum (see ferment (v.)). Figurative sense of "anger, passion" is from 1670s.