E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The herb Monkshood or Wolfsbane. Classic fabulists ascribe its poisonous qualities to the foam which dropped from the mouths of the three-headed Cerbrus, when Hercules, at the command of Eurystheus, dragged the monster from the infernal regions. (Greek, óo, Latin, acontum.)