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
Grozdan	-	Bulgarian, Macedonian
Stephanos	-	Ancient Greek, Biblical Greek, Greek
Dolph	DAHLF	English
Olympia	-	Greek, Slovak
Marjo (1)	MAHR-yo	Finnish, Dutch
Kym	KIM	English (Rare)