know (your) onions

British & Australian, humorous

to know a lot about a particular subject.

That car salesman certainly knew his onions, didn't he?

• too big for boots
• too big for your boots
• too close for comfort
• too close to call
• too for words
• too good to be true
• too hot to handle
• too little, too late
• tools of the trade
• tools of trade
• tools of your trade
• too many chiefs
• too many chiefs and not enough Indians
• Too many cooks .
• Too many cooks spoil the broth.
• too much of a good thing
• too something for words
• top brass
• top dog
• top-drawer
• top-flight
• top flight
• top it all
• top it all off
• top-notch