The phrase "it's no skin off my nose/teeth" is generally used to mean that something isn't much of a risk/concern. But where does it come from? Specifically with respect to teeth. What is tooth skin?
"No skin off my teeth" is not an expression in the UK. Apparently it does exist in the US where it means "no skin off my nose".
Saying "X is no skin off my nose" means that X occurring won't affect you in a positive or negative manner, the outcome will be neutral to you. The phrase is explained by phrase finder as being of boxing origin. I assume because boxers' noses are the body part most prone to damage.
As James McLeod points out "skin of my teeth" means only just or barely. This question addresses its origin.
I'm from the American South, where "no skin off my teeth" is a common phrase. It may be a mixed metaphor, as others have stated; however, it makes sense in that your teeth have no skin and therefore "losing" this nonexistent skin would have no consequence--as in, you can't lose what you don't have. At least that's how I always reasoned it when I would hear the phrase as a youngster.
Looked at in that way, it actually makes more sense than "no skin off my nose." Many Southern Americans have pure British lineage. Perhaps the modern usage in Britain is the mixed metaphor, and the Southern American usage is the same as it was passed down from Colonial Americans? This is all just conjecture on my part. But think about it. It makes sense.
This Ngram suggests no skin off my nose is more common and originated around 1930, and no skin off my teeth around 1940.
Modern proverbs and proverbial sayings from 1989 gives the following:
Cambridge Idioms Dictionary, 2nd ed. gives geographical usage:
No skin off my nose
The earliest "no skin off my nose" I found in Google Books is from a 1910 The Cosmopolitan: Volume 49:
And a 1910 The Saturday Evening Post: Volume 183, Issue 2:
Earlier than this, losing the skin off your nose would happen after a long, tough journey in the sun, or from the intense frost of a cold journey.
No skin off my teeth
Answers to another question here at EL&U suggest the -teeth phrase is a combination of
The earliest "no skin off my teeth" I found in Google Books is from a 1938 The Atlantic monthly: Volume 162:
protected by RegDwigнt♦ Dec 18 '12 at 11:36
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