To keep a secret strictly; to be tight-lipped and not reveal confidential information.
这件事情非常重要，你一定要守口如瓶，不能向任何人泄露。
This matter is extremely important; you must keep it strictly confidential and not disclose it to anyone.
Era:
Ancient
Frequency:
Story:
During the Northern Song Dynasty, the young and promising Fu Bi was recommended by Fan Zhongyan and appointed by Emperor Renzong as the judge of Heyang.
Due to his outstanding political achievements, he was later promoted to prime minister. However, his views on reform clashed with Wang Anshi's, so he resigned from his post as prime minister and returned to his hometown to live in seclusion.
He never casually displayed his emotions (joy or anger), handled affairs fairly, and advocated "keeping one's mouth like a sealed bottle" (守口如瓶) and "guarding one's thoughts like a fortified city" (防意如城).
Next Idiom