late 15c., "begone," literally "move on," from Old French avant "forward!" It is a variant of avant (q.v.).
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avant
French, literally "before," in various terms borrowed into English; cognate with Italian avanti, both from Late Latin abante, a compound of ab "from" (see ab-) and ante "before, in front of" (from PIE root *ant- "front, forehead," with derivatives meaning "in front of, before") which meant "from in front of," but in Vulgar Latin came to mean simply "before."