know (one's) onions

(redirected from know his onions)

know (one's) onions

To be very knowledgeable or skilled in some area. Primarily heard in UK, Australia. I think Nicole is our best candidate for the job—when it comes to corporate accounting, she really knows her onions.
See also: know, onion

know your onions

BRITISH, OLD-FASHIONED
If you know your onions, you know a lot about a particular subject. She really knows her onions in the historical field. Note: This may derive from the rhyming slang `onion rings', meaning `things'.
See also: know, onion

know your onions

be fully knowledgeable about something. informal
Onions is perhaps short for rhyming slang onion rings , meaning ‘things’. The phrase dates from the 1920s.
See also: know, onion
References in periodicals archive ?
And anyone who worked with Sir Alex Ferguson at Manchester United will know his onions.
So does Tim really know his onions when it comes to chilli pickles or are his claims nothing more than bar room bravado?