E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
An animal resembling a weasel, and well worthy of being defended by priest and prince in Egypt, as it feeds on serpents, mice, and other vermin, and is especially fond of crocodiles eggs, which it scratches out of the sand. According to legend, it steals into the mouths of crocodiles when they gape, and eats out their bowels. The ichneumon is called Pharaohs rat.