The term 'One Across the Border' is a reference to the card game UNO, which is a popular game played by two or more players. The objective of the game is to be the first player to get rid of all their cards. Players must match the number or color of the card previously played, and the first player to discard all their cards wins the game. The phrase 'One Across the Border' refers to the first card that a player plays in the game, as it is the first card to cross the imaginary line between the players.