E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Ferrau (in Orlando Furioso).
Ferraute, Ferracute, or Ferragus, a Saracen, son of Lanfusa. He dropped his helmet in the river, and vowed he would never wear another till he had won that worn by Orlando. Orlando slew him with a wound in the navel, his only vulnerable part.