An ace is a playing card, die or domino which has a value of one. It used to mean the side of a die with only one dot. Since this was the lowest roll of the die, it was thought of as 'bad luck' in Middle English. The ace is often the highest playing card, so the meaning has changed to mean good.
- Parlett, David (1990). The Oxford Guide to Card Games. Oxford: Oxford. p. 32.