E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Never sacrifice a white cock, was one of the doctrines of Pythagoras, because it was sacred to the moon. The Greeks went further, and said, Nourish a cock, but sacrifice it not, for all cockerels were sacred either to the sun or moon, as they announced the hours. The
cock was sacred also to the goddess of wisdom, and to Esculapios, the god of health; it therefore represented time, wisdom, and health, none of which are ever to be sacrificed. (See Iamblichus Protreptics, symbol xviii.)