show one's heels

Also, show a clean pair of heels. Run away, flee, as in He wanted to ask her out but she showed her heels before he had a chance, or As soon as the burglar alarm went off, the housebreaker showed a clean pair of heels. The backs of one's heels are exactly what is seen when one is running away, but the allusion of clean is a bit puzzling, unless it is meant in the colloquial sense of “thorough,” as in a clean getaway. [First half of 1500s]