E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Ne sutor, etc. (See COBBLER.)
Stick to the cow. Boswell, one night sitting in the pit of Covent Garden theatre with his friend Dr. Blair, gave an extempore imitation of a cow, which the house applauded. He then ventured another imitation, but failed, whereupon the doctor advised him in future to stick to the cow.