know (one's) beans

To be knowledgable about and/or very familiar with something. I had no idea you were such a good piano player—you really know your beans!

Name	Pronounced	Usage
Boggs
Patrycja	paht-RITS-yah	Polish
Andre	awn-DRAY	English, African American
Matthew	MATH-yoo (English)	English, Biblical
Sophos	-	Ancient Greek
Muadhnait	MOO-nat	Irish