To let the cat out of the bag is to disclose a secret, either deliberately or inadvertently. What's the origin of the phrase 'Let the cat out of the bag'? There are two commonly heard suggested origins of this phrase. One relates to the fraud of substituting a cat for a piglet at markets. If you let the cat out of the bag you disclosed the trick - and avoided buying a pig in a poke (a poke is a type of bag). This form of...

The most popular 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.

What is the Origin of “Let the Cat out of the Bag”? One of the most popular theories as to the origin of the term actually refers to a pig and not a cat. The theory goes that the term originated in a common old English market practice where livestock were often sold and traded in open markets.

The origin of the phrase let the cat out of the bag is not certain. However, there are theories about where it may have come from: One theory has to do with merchants who were looking to make some coin by selling piglets. The young pigs that were sold were put into bags for the customers to carry home.