British Blackjack is a card game that originated in the United Kingdom. It is similar to the American version of Blackjack, but with some slight variations. The main difference is that the dealer stands on all 17s, and the player can double down on any two cards. The term 'COSH' is an acronym for the game, which stands for 'Card On Soft Hand'. This refers to the fact that the player can double down on any two cards, even if one of them is an Ace.