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
Sperantia	-	Late Roman
HanİFe	-	Turkish
Lalla	-	Literature
Fannar	-	Icelandic
DagnÝ	-	Ancient Scandinavian, Icelandic
Stark	[sta:k]