Chinese idiom · 成语
守口如瓶
Meaning
To guard one’s mouth like a bottle; to keep secrets tightly.
Character by character
Origin and story
Buddhist maximAn early exact occurrence is in the Tang Buddhist compilation Fayuan Zhulin (法苑珠林), volume 47, in its discussion of correcting faults. It pairs guarding one’s thoughts like a fortified city with guarding one’s mouth like a bottle. The surrounding passage connects restraint in speech with disciplining the mind and purifying intention.
This is a moral comparison, not an anecdote about someone hiding a message inside a bottle. The narrow opening suggests keeping words securely contained. Later writers applied it specifically to secrecy, as in Sui Tang Yanyi, chapter 35. Today it usually describes someone who will not reveal confidential information, whether from discretion, a promise, or simple refusal to speak.
Sources and further reading
In everyday life
生日惊喜还在准备中，大家都答应守口如瓶，连照片也不发。
The birthday surprise is still being prepared, and everyone has promised to keep it secret—not even posting photos.
Emphasizes revealing nothing; can be approving or frustrated depending on context.