means A sour liquid, mostly dilute acetic acid produced by fermenting wine, cider, or other alcohol, used to flavor and preserve food and to clean.

from Straight from Old French vyn egre, 'sour wine' — vyn (wine) plus egre (sharp, sour), itself from Latin acer, 'sharp,' the same edge you hear in acid and acrid. The name is just chemistry told plainly: wine that went tart, so the French called it exactly that, and English borrowed the label whole.