Understanding the Idiom: "let the cat out of the bag" - Meaning, Origins, and Usage

Idiom language: English
Etymology: (Mid-1700s) The inverse of the idiom pig in a poke. If a dishonest merchant tries to sell a cat as a pig and the cat comes out or is taken out of the bag, the merchant's secret is disclosed.
  • (to let a secret be known): spill the beans, talk, tattle, blab, peach (obsolete), babble, sing

When we speak figuratively, we often use idioms to convey a message in a more colorful and expressive way. One such idiom that is commonly used in English is “letting the cat out of the bag.” This phrase refers to revealing a secret or disclosing information that was meant to be kept hidden.

The origins of this idiom are unclear, but there are several theories about its origin. Some believe it comes from medieval markets where merchants would sell live piglets in bags. Unscrupulous sellers would sometimes substitute a less valuable animal like a cat instead. If someone opened the bag before purchasing, they would “let the cat out of the bag” and reveal the deception.

Regardless of its origin, this idiom has become an integral part of modern English language and is used frequently in both formal and informal settings. It can be used to describe situations where someone accidentally reveals confidential information or when someone intentionally discloses secrets for personal gain.

Origins and Historical Context of the Idiom “let the cat out of the bag”

The origins of idioms can often be shrouded in mystery, but understanding their historical context can provide valuable insight into their meaning. The idiom “let the cat out of the bag” is no exception. While its exact origin is unknown, there are several theories as to how it came to be.

One theory suggests that during medieval times, merchants would sell pigs at markets. To prevent buyers from inspecting the pig before purchase, they would place a cat in the bag instead. If someone were to “let the cat out of the bag,” they would reveal this deceitful practice and ruin the merchant’s reputation.

Another theory suggests that sailors used cats to control rats on ships. When a sailor revealed that a cat was being kept in a bag rather than doing its job, it was said that he had “let the cat out of the bag.”

Regardless of its origin, this idiom has become widely used in modern English language to describe revealing a secret or hidden truth unintentionally or intentionally.

Usage and Variations of the Idiom “let the cat out of the bag”

The idiom “let the cat out of the bag” is a common expression used to describe a situation where someone unintentionally reveals a secret or confidential information. This idiom has been around for centuries and is still widely used today in various contexts.

Variations of the Idiom

Although “letting the cat out of the bag” is a well-known phrase, there are variations that can be used depending on the context. For example, instead of saying “cat,” one might use words like “genie,” “rabbit,” or even “bag.” Similarly, instead of using “out,” one might use words like “spill” or “blab.”

Another variation could be seen in different cultures. In some countries, people may use idioms that have similar meanings but different phrasing. For instance, in French, they say “vendre la mèche” which translates to “sell the wick,” while in Spanish they say “soltar la sopa” which means “to let go of soup.”

Common Usage

The idiom can be used in various situations such as revealing surprise parties or accidentally sharing private information with others. It’s also commonly used when discussing politics or business deals where confidentiality is crucial.

In addition to its literal meaning, this idiom can also be used figuratively to describe any situation where someone reveals something that was meant to remain hidden from others.

Synonyms, Antonyms, and Cultural Insights for the Idiom “let the cat out of the bag”

Have you ever accidentally revealed a secret? If so, you may have let the cat out of the bag. This idiom means to reveal information that was supposed to be kept secret. However, there are other ways to express this idea in English.


There are several synonyms for “letting the cat out of the bag.” One common phrase is “spill the beans,” which means to reveal a secret or confidential information. Another synonym is “blow someone’s cover,” which refers to revealing someone’s true identity or intentions.


On the other hand, if you want to keep a secret safe and secure, you might use an antonym of “letting the cat out of the bag.” For example, you could say that you’re going to “keep mum” about something, meaning that you won’t talk about it at all. Alternatively, if someone asks if they can trust you with sensitive information, you might respond by saying that your lips are sealed.

  • Spill the beans
  • Blow someone’s cover
  • Keep mum
  • Your lips are sealed

Cultural Insights:

The origin of this idiom is not entirely clear. Some sources suggest that it comes from medieval markets where people would sell live animals like pigs or rabbits in bags. Dishonest sellers would sometimes put cats in these bags instead because they were cheaper than other animals. If a buyer opened one of these bags before purchasing it and found a cat inside instead of what they expected, they would have let “the cat out of the bag.”

In some cultures like Japan and China, there are similar idioms involving animals being released from containers. For example, in Japanese, “the monkey is out of the box” means that a secret has been revealed.

Understanding synonyms and antonyms for idioms can help you communicate more effectively in English. By learning about cultural insights related to idioms like “letting the cat out of the bag,” you can also gain a deeper understanding of language and its history.

Practical Exercises for the Idiom “let the cat out of the bag”

In order to fully grasp and utilize the idiom “let the cat out of the bag”, it is important to practice using it in various contexts. The following exercises will help you become more comfortable with this common phrase.

Exercise 1: Conversation Practice

Find a partner and engage in a conversation where you use the idiom “let the cat out of the bag” at least once. Try to make it sound natural and appropriate for your discussion topic. For example, if you are discussing a surprise party, you could say something like “I almost let the cat out of the bag when I accidentally mentioned it to Sarah.”

Exercise 2: Writing Practice

Write a short story or paragraph that includes at least one instance of using “letting the cat out of the bag”. Make sure that your usage fits naturally within your writing and helps convey your message effectively. You could write about someone accidentally revealing a secret or confessing to something they weren’t supposed to.

Note: Remember that idioms should not be taken literally; their meanings often differ from what their individual words suggest.

Common Mistakes to Avoid When Using the Idiom “let the cat out of the bag”

When using idioms in everyday conversation, it’s important to use them correctly in order to avoid confusion and misunderstandings. The idiom “let the cat out of the bag” is no exception. While this phrase may seem straightforward, there are common mistakes that people make when using it.

One mistake is using the idiom in a context where it doesn’t fit or make sense. For example, saying “I let the cat out of the bag about my new car” when you actually just told someone about your new car isn’t quite accurate. This idiom is typically used when someone accidentally reveals a secret or information that was meant to be kept hidden.

Another mistake is misusing the tense of the verb “let”. It’s important to remember that this idiom should always be used in past tense, as it refers to something that has already happened. Saying “I’m going to let the cat out of the bag later” would not be correct usage.

Additionally, some people mistakenly believe that this idiom refers specifically to revealing something embarrassing or shameful. However, this is not necessarily true – it can refer to any kind of secret or information that was meant to be kept private.


  1. “The American Heritage® Dictionary of Idioms”, in (please provide the title of the work)?1, accessed 21 November 2010, archived from the original on 2011-03-18
  2. Gary Martin (1997–), “Let the cat out of the bag”, in The Phrase Finder.
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