Onion was derived from the Old French oignon, which was itself derived from the Latin noun unio. Unlike its French and English progeny, however, the Latin word refers not to the pungent and bulbous herb but to the precious gem we English speakers call a pearl. Interestingly enough, unio shares its stem with the Latin verb unire, which means “to combine many into one,” and some etymologists believe the noun's formal kinship to the verb is an intentional allusion to the fact that both onions and pearls are multilayered objects. (For the record, a pearl is created when an irritant, such as a piece of coral or a parasite, gets inside the shell of a particular type of mollusk and the animal attempts to relieve its discomfort by slowly depositing concentric mineral layers around the offending particle.) In post-classical times, in fact, Roman soldiers used unio as a colloquialism for “onion,” and it is undoubtedly from this slangy sense that the Old French oignon was derived. When the word passed from French to English circa 1130, it was Anglicized to ungeon, but it became unyon around 1356 and later spent a few decades as onyon before the y was changed to i at the beginning of the fifteenth century.
©2013 Michael R. Gates