Posted by ESC on November 17, 2001
In Reply to: Know your onions posted by Julia on November 16, 2001
: Does anyone know the origin of this saying? pls mail me if you do.
Know your onions.
It probably has to do with this meaning of "onions."
ONIONS - (plural noun) business, affairs. 1954. W.G. Smith South St. 297: You just sit here, tend to your onions, let me handle the people what cross me. From the "Random House Historical Dictionary of American Slang, Volume 1, H-O" by J.E. Lighter, Random House, New York, 1994.
Why onions? Mr. Lighter doesn't say. Another definition for "onion" in the same reference is "the head" as in "off one's onion."
While I was looking for "knows his onions" I found this phrase. Doesn't have anything to do with onions, but interesting still:
KNOW ONE'S CANS - "Cowboys on the range in the 19th century were usually starved for reading matter and often read the labels on the cook's tin cans, learning them by heart. A tenderfoot could always be distinguished because he didn't know his cans." From "Encyclopedia of Word and Phrase Origins" by Robert Hendrickson (Facts on File, New York, 1997).