know your onions

US /noʊ jʊər ˈʌnjənz/
UK /noʊ jʊər ˈʌnjənz/
"know your onions" picture
1.

박식하다, 전문가이다

to be very knowledgeable about a particular subject or field

:
You can trust her advice; she really knows her onions when it comes to finance.
그녀의 조언을 믿어도 돼. 금융에 관해서는 정말 박식해.
The mechanic quickly identified the problem, proving he really knew his onions.
정비사는 문제를 빠르게 파악했고, 그가 정말 전문가임을 증명했다.