c.1300, "to trip or miss one's footing" (physically or morally), probably from a Scand. source (cf. dialectal Norw. stumla, Swed. stambla "to stumble"), probably from a variant of the P.Gmc. base *stam-, source of O.E. stamerian "to stammer," Ger. stumm "dumb, silent." Possibly influenced in form by stumpen "to stumble," but the -b- may be purely euphonious. Meaning "to come (upon) by chance" is attested from 1555. Stumbling-block first recorded 1526, used in Rom. xiv.13 to transl. Gk. skandalon. Stumblebum "alcoholic derelict" first recorded 1932.