(Previously, Libra.)
The constellation Scorpio comes from the story of Orion, the hunter. Orion bragged about killing all the animals in Crete, which displeased the goddess Artemis. Artemis was the goddess of hunting, but she was also a wildlife conservationist. She produced a giant scorpion from the earth to sting Orion to death.
There are other myths surrounding Scorpio, but the majority involve some variant of the Orion/Artemis/scorpion story.