If you're a card player who cheats, you might hide an ace card in your shirt sleeve and pull it out so you can win. If you "have an ace up your sleeve," then you have a hidden means of winning...
Origin: Back in the 1500's most people did not have pockets in their clothes, so they kept things in their sleeves. Later on, magicians hid objects up their sleeves and in the 1800's, dishonest card...
The saying, 'to have a card up one's sleeve', derives from gambling with cards, where dishonest players would cheat by concealing certain cards somewhere on their person (often literally up the...