"risk something of value on a game of chance," 1726 (implied in gambling), from a dialectal survival of Middle English gammlen, variant of gamenen "to play, jest, be merry," from Old English gamenian "to play, joke, pun," from gamen (see game (n.)), with form as in fumble, etc. Or possibly gamble is from a derivative of gamel "to play games" (1590s), itself likely a frequentative from game. Originally regarded as a slang word. The unetymological -b- may be from confusion with unrelated gambol (v.). Transitive meaning "to squander in gambling" is from 1808. Related: Gambled; gambling.
"risky venture," 1823, from gamble (v.). As "an act of gambling" by 1879.