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
Sanne	SAHN-nə (Dutch)	Dutch, Danish
Diego	DYE-go	Spanish
Ayishah	-	Arabic
ValdÍS	-	Ancient Scandinavian, Icelandic
Phyliss	FIL-is	English
Yash	-	Indian, Hindi, Marathi, Punjabi, Gujarati, Kannada