The term 'DUMMY, in bridge columns' is a reference to the game of bridge, which is a card game played by four players. In bridge, one of the players is known as the 'DUMMY, ' and they are not allowed to speak or make decisions during the game. The DUMMY's cards are placed face up on the table in two columns, one for each of the other players. This allows the other players to see the DUMMY's cards and use them to their advantage.