E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Proteus (pron. Pro-tuce).
As many shapes as Proteusi.e. full of shifts, aliases, disguises, etc. Proteus was Neptunes herdsman, an old man and a prophet. He lived in a vast cave, and his custom was to tell over his herds of sea-calves at noon, and then to sleep. There was no way of catching him but by stealing upon him during sleep and binding him; if not so captured, he would clude anyone who came to consult him by changing his shape, for he had the power of changing it in an instant into any form he chose.