card up one's sleeve

Idioms and Phrases

Also, ace up one's sleeve . A hidden or secret advantage or resource, as in Before we make a decision, let's see if management has another card up its sleeve , or You can count on John to have an ace up his sleeve . The practice of storing something in one's sleeve dates from the 16th century, when clothes rarely had pockets. The current term comes from gambling, where a dishonest player might so conceal an ace or other winning card. [Mid-1800s]

Example Sentences

His meditated revenge on the prisoners would keep—there was nothing like having a card up one's sleeve.

From Project Gutenberg