c. 1300, "to trip or miss one's footing" (physically or morally), probably from a Scandinavian source (compare dialectal Norwegian stumla, Swedish stambla "to stumble"), probably from a variant of the Proto-Germanic base *stam-, source of Old English stamerian "to stammer," German stumm, Dutch stom "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 1550s. Related: Stumbled; stumbling. Stumbling-block first recorded 1526 (Tindale), used in Romans xiv.13, where usually it translates Greek skandalon.
1540s, "act of stumbling," from stumble (v.). Meaning "a failure, false step" is from 1640s.