The French have a phrase, coq-a-lane, literally, cock to the donkey, which they use in exactly the same sense as we use cock-and-bull; concocted and incredible; fantastic.
A cock and bull story is one that stretches the imaginations somewhat beyond the limits of credulity.
Many learned attempts have been made, both in French and English lore, to discover the precise origin of the phrase, which has appeared in English literature since about boo, but nothing has yet been determined.
Probably it came from a folk tale, one concerning a cock and a donkey, in France, and a cock and a bull, in England. A writer back in 1660, Samuel Fisher, speaks of a cock and a bull being metamorphosed into one animal, but more likely in the original fable the two barnyard animals engaged in conversation.
As no farmer would believe that such conversation was possible, he would be apt to label any incredible tale as a “cock and bull story.”
