Mum's the word
English idiom / From Wikipedia, the free encyclopedia
Mum's the word is a popular English idiom. It is related to an expression used by William Shakespeare, in Henry VI, Part 2.[1]
The word "mum" is an alteration of momme, which was used between 1350 and 1400 in Middle English with very close to the same meaning, "be silent; do not reveal".