have a card up sleeve

have a card up your sleeve

to have an advantage that other people do not know about I still had a card up my sleeve in the form of a letter from his father.

Name	Pronounced	Usage
Dejan	-	Serbian, Croatian, Slovene, Macedonian
Cox	[kɔks]
Dipali	-	Indian, Hindi, Marathi
Sergius	-	Ancient Roman
Marlin	MAHR-lin	English
Shir (2)	-	Persian (Rare)