When you hear the name medusa, the first thought that runs through your mind is of the gorgon. Well, there's more to the word, in the past and present. Medusa is a name as Greek as the myth, but the word goes back to Ancient Greek medein, "to protect" (that's, ironically, just how the name worked out). Probably through Proto-Hellenic, this traces to the Proto-Indo-European root med, which meant "to take measures", since protection requires taking measures to ensure it be so. Med is also the root of the English word mode, through Latin modus and Old French mode. Now, the word Medusa has been in English for a very long time, but a newer definition emerged when Carolus Linnaeus used it to describe a jellyfish species, and indeed the name still exists today. So two descendants of the Greek word for "protector" do exactly the opposite of protecting: one petrifies, the other stuns. Weird.
Adam Aleksic, a freshman studying linguistics at Harvard University, has been described as the internet's sixth most famous etymologist. He has disturbing interests in words, vexillology, geography, board games, limericks, and law, and he loves writing about himself in the third person.
The Etymology Nerd