E. Cobham Brewer 1810–1897. Dictionary of Phrase and Fable. 1898.
Cock and Bull Story.
A corruption of a concocted and bully story. The catch-pennies hawked about the streets are still called cocks—i.e. concocted things. Bully is the Danish bullen (exaggerated), our bull-rush (an exaggerated rush), bull-frog, etc.
1
Another etymology may be suggested
The idol Nergal was the most common idol of the ancient Phœnicians, Indians, and Persians, and Nergal means a dunghill cock. The Egyptian bull is equally notorious under the name of Osi’ris. A cock-and-bull story may therefore mean a myth, in reference to the mythological fables of Nergal and Osiris.
2
The French equivalents are faire un coq à l’âne and un conie de ma mère l’oie (a mother goose tale).
