A game at cards: so called because the players brag of their cards to induce the company to make bets. The principal sport of the game is occasioned by any player bragging that he holds a better hand than the rest of the party, which is declared by saying “I brag,” and staking a sum of money on the issue. (Hoyle.)
“He was a sort of literary Jack Brag.” —T. H. Burton.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
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