English Idiom: “Let the cat out of the bag”

“Never tell Janet anything personal, she always lets the cat out of the bag.”

This happens when someone reveals a secret, usually without intending to. Everyone knows that person who accidentally mentions the surprise party, tells your crush that you like them,  or mentions on Facebook that you are pregnant before you tell anyone. But why a cat and why was it in the bag in the first place?

There are a few different ideas floating around for the origins of this phrase. One suggestion refers to the whip-like “cat o’nine tails” instrument used for punishment in the Royal Navy. When a sailor would reveal the transgressions of another they would remove the (cat) whip from a bag to administer punishment. Another suggests a market scam where customers would think they were buying a pig in a sack, but would get home and discover that they had been fooled into buying a less valuable cat for dinner. There is even a reference of this phrase as far back as 1530, when Johannes Agricola wrote a letter to Martin Luther.

Wherever this phrase originated, we at least know that people have been revealing others’ secrets for many years. Just be sure you don’t let the cat out of the bag before you are supposed to!

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