I find both of the common explanations of "let the cat out of the bag" to be questionable. There have been enough objections to the nautical explanation so let me speak to the "pig" supposition.
How often would a seller be able to dupe his customers before he would be drawn and quartered (or tarred and feathered like the King and the Duke)? How many people would be buying a piglet the size of a cat? How many people would mistake the squealing of a piglet with the yowling of a cat? It doesn't add up.
I would propose that the term would more likely have a trapping or hunting origin where if you are not careful you would let the prey (in this case a cat) escape from a bag or trap. Not so much letting a secret out but just letting something out that you hadn't meant to let out. Any comments?
How often would a seller be able to dupe his customers before he would be drawn and quartered (or tarred and feathered like the King and the Duke)? How many people would be buying a piglet the size of a cat? How many people would mistake the squealing of a piglet with the yowling of a cat? It doesn't add up.
I would propose that the term would more likely have a trapping or hunting origin where if you are not careful you would let the prey (in this case a cat) escape from a bag or trap. Not so much letting a secret out but just letting something out that you hadn't meant to let out. Any comments?