Ever wondered why a cat was in a bag to begin with? Here’s the origin story.
The True Origin of “Let the Cat Out of the Bag”
Updated on Apr. 17, 2025
One of the most curious and funny aspects of language is the use of idioms. These are expressions where the words don’t mean exactly what they say—and they’re often quirky, funny or perplexing, like “spill the beans,“ “break a leg” and “take it with a grain of salt.“ When it comes to odd mental images, few idioms are more amusing than “let the cat out of the bag”—and its origin is just as curious.
When we say “let the cat out of the bag,” we’re not actually talking about a feline that was in a bag (hopefully!) but about a secret or surprise that was revealed. Wondering how a cat in a bag became a metaphor for spilled secrets? We’re tracing the history of the idiom right here.
What’s the origin of “let the cat out of the bag”?
Before diving into theories about this phrase’s origin—we’re talking medieval scams and naval connections—it helps to look at the earliest known use of the phrase. In a 1760 book review in London Magazine, the reviewer complained that he “wished that the author had not let the cat out of the bag,” presumably referring to some kind of plot point.
But while the first recorded use of the phrase is pretty straightforward, the actual “cat out of the bag” meaning and origin remain murky. That’s common with idioms, simply because of the way language evolves. People start using phrases gradually, over time, and there’s no concrete historical record of how they came up with that phrase. This is especially the case with figurative expressions, which, by definition, don’t literally mean what they say.
So there’s no definitive consensus as to where it comes from, but there is an explanation that most linguists consider at least somewhat likely. And it actually, literally, involves cats in bags!
Could “let the cat out of the bag” be linked to a medieval scam?
The most heavily cited explanation for why we say “let the cat out of the bag” dates back to the Middle Ages. As the story goes, shady livestock vendors in medieval marketplaces sought to swindle their buyers. When someone would purchase a pig, the vendor would sneak a cat into the bag instead, cheating the buyer out of the higher price for a pig. It wasn’t until the buyer arrived home and, literally, let the cat out of the bag that they’d realize they’d been scammed, hence the phrase’s association with revealing a secret.
This explanation isn’t definitively proven, and there’s no evidence that medieval vendors actually carried out such a scam on a regular basis. (Snopes, in fact, casts it as an outright falsehood, pointing out that the significant weight difference between a pig and a cat would make such a scam impossible even without the buyer seeing the critter.)
But this explanation does have some things going for it. As Gary Martin, the creator of Phrase Finder and a writer with 26 years of experience researching phrases and idioms, points out, both the Dutch and German versions of this phrase translate to “to buy a cat in a bag,” which alludes more directly to a deceitful purchase. And the Spanish translation means “to give a cat for a hare,” suggesting (somewhat more plausibly) that vendors would switch rabbits, not pigs, with the cats.
But there’s more to this bit of idiom history trivia. The expression “pig in a poke” also refers to making a deal or purchasing something without fully validating it. Merriam-Webster says the first known use of the phrase was in 1555, but the terms have been in use even longer: The Oxford English Dictionary traces the use of pig back to the Old English period (pre-1150), and a poke, an old-timey word for a “bag,” to around 1300.
Does the phrase have nautical roots?
There’s another theory about the origins of this expression, and it’s a good deal darker. This explanation claims that the “cat” the expression refers to is not a feline but the “cat o’ nine tails,” a whip made from nine intertwined cords that was used as a form of punishment in the British Royal Navy and in prisons until as late as the 1840s. It was called a “cat” because the marks it left on its victims resembled scratches. (In fact, it’s also a likely candidate for the origin of “cat got your tongue.”)
But there are reasons to question whether this theory really holds up. For one thing, there are no records of the actual phrase “let the cat out of the bag” being used in reference to nautical exploits. Not to mention that the cat o’ nine tails punishment, while certainly notorious and unpleasant, wasn’t really a secret, per se.
How did “let the cat out of the bag” become part of everyday English?
So how did this quirky phrase find its way into daily English conversation? Today I Found Out has a far simpler explanation: It’s stinking hard to get a cat that was let out of a bag back into said bag. The theory suggests that “let the cat out of the bag” was nothing more than an artsy use of figurative language, comparing a widely known secret to a loosed cat. Maybe there never was a cat in a bag—linguists may just be massively overthinking things!
Do other languages have a version of “let the cat out of the bag”?
As it turns out, English isn’t the only language to use animals in idioms and phrases. There are variations of “let the cat out of the bag” used in several other languages and cultures.
- Vendre la mèche (French): This French phrase literally means “to sell the fuse,” but don’t let that throw you—it has nothing to do with fireworks. Instead, it means spilling a secret. The fuse symbolizes secret intel, and once it’s sold, the secret’s out.
- Die Katze aus dem Sack lassen (German): Germans share this phrase with English speakers. Die Katze aus dem Sack lassen translates directly to “let the cat out of the bag.” It’s used the same way too: to disclose information that was meant to be kept under wraps.
- Lòu chū mǎ jiǎo (Mandarin Chinese): The literal translation of this saying is to expose a horse’s leg. But just like the cat, the phrase has nothing to do with horses. The phrase refers to someone accidentally exposing their true intent or identity.
Why trust us
At Reader’s Digest, we’re committed to producing high-quality content by writers with expertise and experience in their field in consultation with relevant, qualified experts. We rely on reputable primary sources, including government and professional organizations and academic institutions as well as our writers’ personal experiences where appropriate. We verify all facts and data, back them with credible sourcing and revisit them over time to ensure they remain accurate and up to date. Read more about our team, our contributors and our editorial policies.
Sources:
- Today I Found Out: “Where Did The Expression ‘Let The Cat Out Of The Bag’ Come From?”
- Mental Floss: “What’s the Origin of ‘Let the Cat Out of the Bag’?”
- Snopes: “What’s the Origin of ‘Letting the Cat Out of the Bag’?”
- Phrase Finder: “The meaning and origin of the expression: Let the cat out of the bag”
- Phrases.org: “The meaning and origin of the expression: A pig in a poke”
- The Connexion: “Learning French: the origins and meaning of vendre la mèche”
- Cambridge Dictionary: Translation of die Katze aus dem Sack lassen
- Chinese Language Guide: “To Expose a Horse’s Leg – Fun Chinese Sayings”
- Oxford English Dictionary: “Where does the noun pig come from?”
- Merriam-Webster: “Pig in a poke”
