onion

Etymology

From Middle English onyoun, oynoun, from Old French oignon, from Latin ūniōnem, accusative of ūniō (“onion, large pearl”), which had also been borrowed into Old English as yne, ynnelēac (“onion”) (> Middle English hynne-leac, henne-leac). Also displaced Middle English knelek (literally “knee-leek”) and the inherited term ramsons.

noun

1. A monocotyledonous plant (Allium cepa), allied to garlic, used as vegetable and spice.
2. The bulb of such a plant.
   dorrẹ̅, dōrī adj. & n. […] cook. glazed with a yellow substance; pome(s ~, sopes ~. […] 1381 Pegge Cook. Recipes p. 114: For to make Soupys dorry. Nym onyons […] Nym wyn […] toste wyte bred and do yt in dischis, and god Almande mylk. 1962 (quoting 1381 text), Hans Kurath & Sherman M. Kuhn, eds., Middle English Dictionary, Ann Arbor, Mich.: University of Michigan Press, ISBN 978-0-472-01044-8, page 1242
3. A plant of the genus Allium as a whole.
4. (slang, of a drug) An ounce.
5. (obsolete baseball slang) A ball.
6. (obsolete, slang) A watch-seal.
   […] M was a Magsman, frequenting Pall-Mall; / N was a Nose that turned chirp on his pal; / O was an Onion, possessed by a swell; / P was a Pannie, done niblike and well. […] 1846, George William MacArthur Reynolds, The Mysteries of London, page 60
7. Alternative letter-case form of Onion (“an inhabitant of Bermuda; a Bermudian”)