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
Heleen	hay-LAY:N	Dutch
Gregor	GRE-gawr (German)	German, Scottish, Slovak, Slovene
Lumusi	-	Western African, Ewe
BÉAtrice	-	French
Roselyn	ROZ-ə-lin	English
Vjekoslav	-	Croatian