bobble (v.)

"move up and down with a short, jerking motion," late 14c., bobben, probably connected to the Middle English bobben that meant "to strike in cruel jest, beat; fool, make a fool of, cheat, deceive" (early 14c.), which is perhaps from Old French bober "mock, deride," and perhaps ultimately of echoic origin. Related: Bobbed; bobbing. The sense of "snatch with the mouth something hanging or floating," as in bobbing for apples (or cherries), is recorded by 1799. To bob and weave in boxing is by 1928. Compare bob (n.2).