gamble: [18] Although its ancestry has never been established beyond all doubt, it seems overwhelmingly likely that gamble is essentially the same word as game (in which the sense ‘gamble’ is preserved in such contexts as gaming tables and betting and gaming). The Middle English form of game was gamen, and it is thought that this may have produced a variant form gamel (recorded in the 16th century) which in due course became gamble. => game
gamble (v.)
"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 intrusive -b- may be from confusion with unrelated gambol (v.). Transitive meaning "to squander in gambling" is from 1808. Related: Gambled; gambling.
gamble (n.)
"risky venture," 1823, from gamble (v.). As "an act of gambling" by 1879.