know stuff

know one's stuff

and know one's onions

to know what one is expected to know. I know my stuff. I can do my job. She can't handle the assignment. She doesn't know her onions.

to know a lot about a subject or be an expert at doing something When it comes to restoring grand pianos, he really knows his stuff.

(informal)

to know a lot about a subject, or to be very good at doing something When it comes to restoring grand pianos, Mr Morley really knows his stuff.

Name	Pronounced	Usage
Nettie	['neti]
Esben	-	Danish, Norwegian
Orvokki	OR-vok-kee	Finnish
Cosmina	-	Romanian
Platt	[plæt]
Usman	-	Arabic