To let the cat out of the bag verb phrase
To unintentionally reveal secret or private information
Promise me you won't let the cat out of the bag.
I'm really sorry! I didn't want to let the cat out of the bag but I had no other choice.
I let the cat out of the bag and ended up telling them everything.
To talk freely and unintentionally disclose private information or secret to others
To accidentally reveal what you are going to do or what you believe
1. To stop talking or thinking about something.
2. To unintentionally disclose important or confidential information.
To reveal, usually in an unintentional way
The verb "let" should be conjugated according to its tense.
The origin of this phrase is vague but there are theories about where it may have come from.
One theory refers to a multi-tailed whip that was called a "cat o' nine tails" used by the Royal Navy as an instrument to punish sailors. The whip, or "the cat" had to be kept in a bag to protect its leather from drying out in the salty sea air. When a sailor receives punishment, "the cat" would be taken out of the bag, hence the phrase.
The other theory comes from the livestock markets. When a customer bought live piglets, the merchant would put it into a bag for easier transport. However, the merchant would sometimes swap the pig for a cat when the customer looked away to make some coin. The customer wouldn't find out about this until they got home and literally let the cat out of the bag.
Moreover, this phrase first appeared in a 1760 edition of The London Magazine:
“We could have wished that the strange genious, author of this piece, had not let the cat out of the bag; for it is such a mad, ranting, swearing, caterwauling pus*, that we fear no sober family will be troubled with her.”