to know one's onions

āχāĻ‚āϰ⧇āϜāĻŋāϤ⧇ "know one's onions"āĻāϰ āϏāĻ‚āĻœā§āĻžāĻž āĻ“ āĻ…āĻ°ā§āĻĨ

01

to have a great deal of information regarding a particular subject

to [know] {one's} onions definition and meaning
Idiom
Informal
āωāĻĻāĻžāĻšāϰāĻŖ
When it comes to repairing vintage cars, John really knows his onions; he can fix anything under the hood.
LanGeek
āĻ…ā§āϝāĻžāĻĒ āĻĄāĻžāωāύāϞ⧋āĻĄ āĻ•āϰ⧁āύ