- bet
- 1590s, in the argot of petty criminals; probably aphetic of abet, or from obsolete beet "to make good," from O.E. bętan "make better, arouse, stimulate," from P.Gmc. *baitjanan. The original notion is perhaps "to improve" a contest by wagering on it, or it is from the "bait" sense in abet. Used since 1852 in various Amer.Eng. slang assertions (cf. you bet "be assured," 1857). Related: Betting.