An expression used when tossing a coin to decide between two alternatives, as in Let's just flip a coin to decide who pays—do you want heads or tails? Each person involved chooses a different side of the coin, either “heads” or “tails,” and whichever side lands facing up is considered the winner. This usage, dating from the late 1600s, is sometimes turned into Heads I win, tails you lose, meaning “I win no matter what,” which probably originated in an attempt to deceive someone. [Mid-1800s]