'Heels' in the Bible

Dan shall be a serpent by the way, an adder in the path, that biteth the horse heels, so that his rider shall fall backward.

Thou puttest my feet also in the stocks, and lookest narrowly unto all my paths; thou settest a print upon the heels of my feet.

Wherefore should I fear in the days of evil, when the iniquity of my heels shall compass me about?

And if thou say in thine heart, Wherefore come these things upon me? For the greatness of thine iniquity are thy skirts discovered, and thy heels made bare.