Where The Phrase 'Cat's Out Of The Bag' Came From
When a secret comes to light, someone involved in the revelation might say "The cat's out of the bag" to indicate that what used to be privileged information is now public knowledge. If you stop to think about the phrase literally, things get confusing and funny pretty quickly. Where did this phrase come from in the first place? Was there an actual, confidential feline in some sort of enclosure that got out, thus ruining some sort of surprise, and if so, can we get a backstory to this bizarre situation?
According to Reader's Digest, the first recorded instance of the saying dates back to a 1760 book review in the periodical London Magazine in which the reviewer wrote that he "wished that the author had not let the cat out of the bag," presumably meaning that there was an important plot point revealed too soon in the course of the story. While this may indicate the time period in which the phrase entered common parlance in British popular culture, it doesn't explain why the saying came to be in the first place.
Snopes, a website devoted to fact-checking and dispelling commonly held myths, misconceptions, and urban legends, notes two possible origins for the odd expression. One involves the unsavory practice of a crooked livestock salesperson placing a cat in a bag and selling it to an unlucky customer who believes they are purchasing a pig. Upon returning home, the duped buyer would open the bag, discover a cat where a pig should be, and lo and behold, "the cat's out of the bag"!
Was there ever a literal cat let out of a literal bag?
According to Snopes, this origin of the phrase is very unlikely for several reasons. First, it's unlikely that someone expecting a pig would receive a bag with a cat in it and not immediately know something was wrong; pigs and cats don't resemble or behave like each other at all, even inside a bag. Second, for this phrase to become so well known, the "substitute a cat for a pig" scam would have had to have worked many, many times. Considering the first reason, the second seems even more dubious.
The second possible origin of the saying comes from maritime history. The Wessex Museums explains that the British Royal Navy kept a whip known as a "cat-o'-nine-tails" on ships for disciplining unruly or incompetent sailors. The whip was supposedly stored in a red sack, and therefore, when it was extracted for use, the "cat" was out of the "bag." Once again, however, this origin story is likely a fable, as there's no proof that cat-o'-nine-tails were actually stored in special sacks, nor that the phrase originated in the naval community.
The actual etymology of "the cat's out of the bag" is unclear. Snopes posits that it's simply a good metaphor for a secret getting out — a cat leaping out of a bag is explosive, surprising, and goes where it wants to go despite the "bag holder's" wishes. Humor writer Will Rogers was indeed correct when he quipped, per Today I Found Out, "Letting the cat out of the bag is a whole lot easier than putting it back in."