Don't breathe a word and Mum's the word

Mum's the word and don't breathe a word are semantically related In some cases you can replace phrase "Mum's the word" with "Don't breathe a word", this phrases are similar.

Don't breathe a word and mum's the word are semantically related in say nothing topic. Sometimes you can replace phrase "Don't breathe a word" with "Mum's the word", this phrases are similar.