Writers describing hair-raising adventures and dangerous situations from which an escape is, somehow, miraculously effected, are often known to use the phrase "by the skin of his teeth" when doing so, but one man who has used this phrase had to stop and think about it recently, when he realized that teeth don't have skin.
Moys Kenwood, a scribbler at satirical news website TheSpoof.com has used the phrase in his writing and in general speech, but was forced to check himself and reconsider his alternatives when he discovered this fact.
"As anybody capable of conducting a rudimentary googlesearch will know, teeth consist of pulp, dentin, enamel and cementum, and not, crucially, skin. Therefore, the phrases 'by the skin of my teeth', 'by the skin of your teeth', 'by the skin of his teeth', 'by the skin of her teeth', 'by the skin of its teeth', 'by the skin of our teeth', 'by the skin of their teeth', and so on, are rather misleading, and, for purposes of accuracy, wholly inaccurate."
It's not known where the phrase 'by the skin of one's teeth' originally came from, but it could initially have sprung up in the Fantasmolithic Period, more than 300 million years ago, when things were very different, and the teeth of some creatures may have been covered in skin.