# mum's the word

idiom

Source: https://englishreference.com/idiom/mums-the-word
Updated: 2026-08-10

## Meaning

Indicates that something is a secret and not to be divulged.

## Examples

- I have a surprise for him, so mum's the word.
- I am leaving my job soon, but mum's the word for now.
- If you find the hidden cookies, remember that mum's the word.
- We are planning a surprise party for our boss, but remember that mum's the word until Friday.
- I know you saw who broke the window, but mum's the word because I do not want to get our friend in trouble.
- The doctor told me the baby's gender today, and since my husband wants a surprise, mum's the word during dinner.
- We found a cheaper way to fix the car, but mum's the word so the mechanic does not raise his prices next time.
- 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.

## Origin

First recorded in 1704, the expression is derived from the Middle English *mum*, a representation of the sound made with a closed mouth to signal silence. The term functioned as a directive to remain quiet long before the full phrase became a standard idiom.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.