In Ancient Greece a Gorgoneion (or stone head, engraving, or drawing of a Gorgon face, often with snakes protruding wildly and the tongue sticking out between her fangs) frequently was used as an apotropaic symbol and placed on doors, walls, floors, coins, shields, breastplates, and tombstones in the hopes of warding off evil.
Medusa was a monstrous chthonic female character of the Gorgon race; gazing upon her would turn onlookers to stone. She was beheaded by the hero Perseus, who thereafter used her head as a weapon, until giving it to the goddess Athena to place on her shield.
The concept of the Gorgon is at least as old in mythology as Perseus and Zeus. The name is Greek, being derived from “gorgos” and translating as terrible or dreadful.