"jellyfish," 1758, as genus name, from the name of one of the three Gorgons with snakes for hair, whose glance turned to stone him who looked upon it (attested in English from late 14c.). Her name is from Greek Medousa, literally "guardian," fem. present participle of the verb medein "to protect, rule over" (from PIE root *med- "take appropriate measures"). The zoological name was chosen by Linnæus, suggested by the creature's long tentacles. Related: Medusoid.