Long ago, the Romans were at war with the Sabines. Romulus, the king of Rome, appointed a general named Tarpeius to defend the city.
Tarpeius, meanwhile, had a daughter named Tarpeia who loved nothing more than pretty jewelry made of silver or, even better, gold. One day, Tarpeia was watching the battlefield from the city's walls and she noticed that the Sabine soldiers wore beautiful golden bracelets on their left arms. "Oh," she sighed, "I would do anything to have a bracelet like that!"
Desperate to get one of the bracelets, Tarpeia snuck out of the city and entered the enemy camp. She met with the Sabine king and offered to betray the city of Rome in exchange for a reward. The king was delighted. "Just name your price," he said. Tarpeia smiled and replied, "I want what the Sabine soldiers wear on their left arms," by which she meant their bracelets. The king agreed and arranged for Tarpeia to let the Sabine army into the city that night.
As soon as it was dark, Tarpeia went to one of the city's gates and opened the door to the Sabines as promised. "But before you enter the city," she insisted, "you must give me what you are wearing on your left arms!" The Sabines laughed and tossed their bracelets to Tarpeia, but then they crushed her with their shields, which they also carried on their left arms, thus punishing her for having betrayed her own people.
The Romans later found Tarpeia's body and realized what she had done, so they took her corpse and hurled it from a high cliff which they named "The Rock of Tarpeia." For ever after, traitors were punished by being hurled to their death from that same rock.