E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
So called from Tarpeia, a vestal virgin, the daughter of Spurius Tarpeius, governor of the citadel on the Capitoline Hill. Tarpeia agreed to open the gates to the Sabines if they would give her what they wore on their arms (meaning their bracelets). The Sabines, keeping their promise to the ear, crushed her to death with their shields, and she was buried in that part of the hill called the Tarpeian Rock. Subsequently, traitors were cast down this rock and so killed.