Idiom - Let the cat out of the bag

Let the cat out of the bag:

If you let the cat out of the bag, you let someone know a secret.

We'd planned a surprise party for Donna, but some guy she works with let the cat out of the bag, so now she knows.

Don't forget that this is a secret, so whatever you do, don't let the cat out of the bag.

Persian:
لو دادن

Origin: Possibly related to the fact that in England in the Middle Ages, piglets were usually sold in bags at markets. Sometimes, someone would try to cheat a buyer by putting a cat in one of the bags instead of a piglet. And if someone let the cat out of the bag, the fraudster's secret was revealed.

Proverb - A Cat May Look at a King

A Cat May Look at a King:

An inferior isn't completely restricted in what they may do in the presence of a superior.