French, literally "mouth" (Old French boche, 11c.), from Latin bucca "cheek," which in Late Latin replaced os (see oral) as the word for "mouth" (and also is the source of Italian bocca, Spanish boca). De Vaan writes that "The meaning 'mouth' is secondary, and was originally used in a derogatory way." It is perhaps from Celtic, Germanic, or a non-IE substrate language. Borrowed in English in various senses, such as "king's allowance of food for his retinue" (mid-15c.); "mouth" (1580s); "metal plug for a cannon's vent" (1862; verb in this sense from 1781).