What it means
Means you’ve accidentally revealed a secret you were meant to keep, usually by talking too much or messaging the wrong person. Once it’s out, you can’t un-say it and the surprise is basically dead. It’s an old, widely used idiom, and nobody’s actually stuffing cats in bags, thankfully. Use it for gossip, surprises, office drama, whatever.
Usage examples
"We’d planned a surprise do for Jess, but Liam let the cat out of the bag by dropping it in the family group chat."
"She let the cat out of the bag about the party before we'd even sent the invites."
"Don't let the cat out of the bag, the promotion isn't official yet."
"I nearly let the cat out of the bag when his mum asked why we all kept Saturday free."
"Mate, keep it zipped till Friday. If you let the cat out of the bag now, the whole birthday plan's cooked."
Where it comes from
This idiom goes back centuries. It’s commonly linked to old market fraud, where a seller was meant to hand over a piglet in a bag but swapped in a worthless cat instead. If the bag got opened too soon, the trick was exposed and the secret was out. The exact historical proof is debated, but that’s the standard recorded origin story.
Other ways to say it
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