From the Greek
Μεδουσα (Medousa), which was derived from
μεδω (medo) meaning "to protect, to rule over". In Greek myth this was the name of one of the three Gorgons, ugly women who had snakes for hair. She was so hideous that anyone who gazed upon her was turned to stone, so the hero
Perseus had to look using the reflection in his shield in order to slay her.