call someone’s bluff, to

To uncover a deception, or challenge someone to carry out a threat or prove a dubious point. The term comes from poker, where the players bet as to who has the best poker hand of them all. To bluff is to bet on a hand one does not believe is the best; to call means to match a bet, that is, bet an equivalent amount. When the cards are uncovered, whoever has the best hand wins the entire pot (all the money the players have put up). The term is American in origin and dates, like American poker, from the early 1800s. It was being transferred to other pursuits by the late nineteenth century; “Where shall we be when that bluff is called,” reads an entry in the Congressional Record (March 1896).