late 14c., "process of making bread," verbal noun from bake (v.). Baking powder "yeast substitute" is from 1850.
early 15c., from Old French ferment (14c.), from Latin fermentum "leaven, yeast; drink made of fermented barley;" figuratively "anger, passion" (see ferment (v.)). Figurative sense of "anger, passion, commotion" in English is from 1670s.
It forms all or part of: barm; barmy; bourn (n.1) "small stream;" braise; bratwurst; brawn; brawny; braze (v.1) "to expose to the action of fire;" brazier; Brazil; bread; breed; brew; broth; broil (v.2) "to quarrel, brawl;" brood; effervesce; effervescence; effervescent; embroil; ferment; fervent; fervid; fervor; imbroglio.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit bhurnih "violent, passionate;" Greek phrear "well, spring, cistern;" Latin fervere "to boil, foam," Thracian Greek brytos "fermented liquor made from barley;" Russian bruja "current;" Old Irish bruth "heat;" Old English breowan "to brew," beorma "yeast;" Old High German brato "roast meat."