0949 Mum's the word - English Idioms

Explanation

Keep silent about something; keep it a secret. It's an instruction or agreement to not reveal information.

Origin

Mum likely derives from the closed-lip humming sound mmm, indicating silence, or Middle English momme (silence).
The phrase appears in Shakespeare's *Henry VI, Part 2* (late 16th century): Seal up your lips and give no words but mum.
It implies sealing one's lips.

Alternatives

Slang/Informal:

Keep it on the DL (Down-Low)
Zip it / Button it
Keep schtum (UK)
Don't spill the beans (Don't reveal the secret)
Keep this on the low

Vulgar/Emphatic (Stronger commands):

Keep your fucking mouth shut.
Don't breathe a goddamn word.
Tell anyone and you're dead. (Hyperbolic threat)

Milder/Standard:

Please keep this confidential.
Let's keep this between ourselves.
Don't reveal this information.

Situational Appropriateness

Mostly informal. It can sound slightly quaint or playful.
Might be too informal for a very serious business or legal context requiring confidentiality, where keep this confidential would be preferred.

Misunderstanding Warnings

A learner might be confused by the word Mum (mother). The connection to silence (mmm) needs to be understood.

Examples

We're planning a surprise party for Sarah, so mum's the word!
Don't tell anyone you saw me here – mum's the word.
A: Should I mention this to anyone? B: No, definitely not. Mum's the word.

Dialogue

Person A: I accidentally found out who got the promotion, but it hasn't been announced yet.

Person B: Ooh, juicy! Who is it?

Person A: I can tell you, but seriously, mum's the word until Friday.

Person B: Okay, okay, mum's the word. Spill the beans!

Response Patterns

Got it. / Understood.
My lips are sealed.
Okay, I won't say a thing.
Secret's safe with me.
You got it, mum's the word.

Common Follow-up Questions/Actions

The person instructed usually confirms understanding: Okay, won't breathe a word.
The person giving the instruction might reiterate: Seriously, don't tell anyone.
If the reason for secrecy isn't clear, one might ask: Okay, but why?

Conversation Starter

No. It's an instruction or agreement made during a conversation about keeping something secret.

Intonation

Often said in a slightly lowered, conspiratorial, or firm tone.
Emphasis typically on Mum's.
MUM'S the word.
Sometimes accompanied by a finger-to-lips gesture (shhh).

Generation Differences

Widely understood by all generations, though it might feel a bit old-fashioned to some younger people. Still commonly used.

Regional Variations

Common in both British English and American English.

Off the record

🎲 Keep it on the down-low

[0949] Mum's the word