You probably knew this expression, to let the cat out of the bag:
It is used when someone tells something that was supposed to be secret. No one can explain how the cat got into the bag. But there is an old story about it.
Long ago tradesmen sold things in large cloth bags. One day a woman asked for a pig. The tradesman held up a cloth bag with something moving inside it. He said it was a live pig. The woman asked to see it. When the dishonest tradesman opened the bag, out jumped a cat – not a pig. The tradesman’s secret was out. He was trying to trick her. And now everybody knew it.
We have a secret and this has some kind of relation with the definition given above. But we’re not letting the cat out of the bag just yet. Keeping you waiting ;-)
Have a great Caturday!
Texas, a cat in New York 