the.com/fermentation

means The chemical process by which yeasts, bacteria, or other microbes break down sugars and other compounds without oxygen, producing things like alcohol, acids, or gases as a byproduct.

from From Latin fermentum, 'leaven' or 'that which causes rising,' itself tied to the verb fervere, 'to boil.' That connection isn't poetic exaggeration — a vat of fermenting grape must or dough genuinely seems to bubble and seethe as if over heat, even though no fire is involved. The word passed through French into English keeping that same sense of restless, working activity.