I have a surprise for him, so mum's the word.
mum's the word
idiomIndicates that something is a secret and not to be divulged.
Origin
first recorded 18th c.From mum (“silence”). Recorded since 1704.
We are planning a surprise party for our boss, but remember that mum's the word until Friday.
She whispered the details of the confidential merger to her partner, adding that mum's the word until the official announcement is made to the press.
- 01
bad word
A vulgar word.
- 02
breathe a word
To divulge even part of a secret (usually used with a negative).
- 03
dicky
[Cockney slang]word
- 04
dirty word
The name of a topic that a person prefers not to hear or discuss.
- 05
empty words
Any type of talk with little meaning; a message that seems to contain meaningful content but is actually vapid.
- 06
from the word go
From the very beginning; from the outset; immediately upon starting.
- 07
get the word out
To make some information more widely known.
- 08
hang on every word
To be completely attentive to what another person is saying.
Last updated July 12, 2026