means A round, layered bulb vegetable with a pungent flavor and aroma, used as a staple in cooking around the world.

from From Old French 'oignon,' which traces back to Latin 'unionem' (accusative of 'unio'). That Latin word meant both 'a single large pearl' and 'onion' — a farmer's metaphor, since both are single rounded things made of layers. The 'one-ness' idea comes from 'unus,' Latin for 'one,' making 'onion' a distant cousin of 'union' and 'unity' — a vegetable named for being all of one piece, even as it peels apart in your hands.