The Grammarphobia Blog

Like the back of one’s hand

Q: From a Canadian television commercial: “The monks of Oka, Quebec, knew how to make cheese like the back of their hand.” What do you think? It doesn’t sound right to me.

A: We agree that the Canadian commercial is oddly phrased. It’s odd for several reasons.

First, the expression “like the back of one’s hand” is more familiar when used in the singular—“like the back of my (or his or her) hand.”

The imagery is out of kilter in the plural “backs of their hands”—and even more out of it in the illogical mixing of singular and plural in “back of their hand,” the version on Canadian TV.

Second, a person generally knows something—not how to do something—“like the back of his hand.”

As the Oxford English Dictionary explains, the verb “know” in the expression refers to “a thing, place, or person.”

So we’d say, “He knows French like the back of his hand,” not “He knows how to speak French like the back of his hand.”

Finally, a literal-minded person might interpret the commercial to be saying the monks knew how to make cheese that resembled the backs of their hands. Or, as one viewer of the commercial commented online, “old, wrinkly, and smelly.”

The OED says that “to know (something) like the back of one’s hand” means “to be thoroughly familiar or conversant with.”

While the expression sounds venerable, Oxford has no published examples older than the mid-20th century. Here are the OED’s citations, all from mystery or suspense novels.

“I know him as well as I know the back of my hand.” (From Margaret Millar’s Wall of Eyes, 1943.) 

“I know that book like the back of my hand.” (From Michael Innes’s The Weight of Evidence, 1944.)  

“I know the district like the back of my hand.” (From Mary Stewart’s Wildfire at Midnight, 1956.)

“I know that photograph like the back of my hand.” (From Catherine Aird’s Henrietta Who? 1968.)

We’ve spotted a few earlier examples, though.

For instance the expression appears twice in John Collis Snaith’s novel The Sailor, first published in 1916:

“So much had he knocked about the world that he knew men and cities like the back of his hand” … “his native city of Blackhampton, certain parts of which he knew like the back of his hand.”

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