In Greek mythology, Medusa was a monster that had the appearance of a woman with snakes for hair. Anyone who looked directly at her would be so horrified that they would turn to stone. The name of the Medusa spiders is a reference to this. The spiders can paralyze with their bite, to the point where not even a doctor can tell you're alive.
The Medusa Spider was also in the movie Anaconda: The Hunt for the Blood Orchid, in which a greedy guy like Nikki uses a Medusa spider to bite his partner.