know one's stuff

Also, know one's onions. Be experienced or knowledgeable in one's field or in the matter at hand. For example, Patrice knows her stuff when it comes to Mexican history, or We need a handyman who knows his onions. The allusion in the variant is unclear. [First half of 1900s]

Common Names:

Name	Pronounced	Usage
Birgir	-	Ancient Scandinavian, Icelandic
ÉMilien	e-meel-YAWN	French
Stavros	-	Greek
Maximiliane	-	German
Dietlinde	deet-LIN-də	German
Finn (2)	FIN (Danish)	Danish, Norwegian, Swedish