Wiktionary
breathe a word
vb. (context idiomatic English) to divulge a secret (usually used with a negative)
Usage examples of "breathe a word".
She had yet to breathe a word of her plan to the children or the servants.
This blasted puncture is smack in the middle of his cabin wall, and if you breathe a word about it to him, I'll skin you.
I made a promise I wouldn't breathe a word about your shenanigans.
I have given my word to the old General not to breathe a word to anyone but the Allied High Command in person.
Did she breathe a word to you about this sudden inclination to devote herself to the nunnery?
Nor could he afford to breathe a word of his suspicions to anyone.