"move with a short, jerking motion," late 14c., probably connected to Middle English bobben "to strike, beat" (late 13c.), perhaps of echoic origin. Another early sense was "to make a fool of, cheat" (early 14c.). Related: Bobbed; bobbing. The sense in bobbing for apples (or cherries) recorded by 1799.

"act of bobbing," 1540s, from bob, v.1. As a slang word for "shilling" it is attested from 1789, but the signification is unknown.

"short hair," 1680s, attested 1570s in sense of "a horse's tail cut short," from earlier bobbe "cluster" (as of leaves), mid-14c., a northern word, perhaps of Celtic origin (compare Irish baban "tassel, cluster," Gaelic babag). Used over the years in various senses connected by the notion of "round, hanging mass," such as "weight at the end of a line" (1650s). The hair sense was revived with a shift in women's styles early 20c. (verb 1918, noun 1920). Related words include bobby pin, bobby sox, bobsled, bobcat.