Idiom meaning, usage examples, facts

1. When Rachel decided she was going to quit her job, she told her best friend but she didn’t want to let the cat out of the bag. Rachel told her friend not to tell anyone.
2. The children put their money together to buy their mother a birthday present, but the youngest child became excited and couldn’t keep from telling his mother what they had bought. His brothers and sisters told him he shouldn’t have let the cat out of the bag.

Synonym: spill the beans. Antonym: keep (something) under (one’s) hat. Centuries ago, merchants would sell piglets in bags. If a dishonest merchant placed a cat in the bag instead of the more costly and valuable piglet, the buyer might not know until they opened the bag and let the cat out