1242 My lips are sealed - English Idioms

Explanation

A promise to keep something secret.
Indicates that the speaker will not reveal the information they have been told or have discovered.

Origin

My lips are sealed: A direct metaphor – closing one's lips physically prevents speaking. The phrase emphasizes this commitment to silence. Dates back to at least the 19th century. Often accompanied by the gesture of drawing a zipper across the lips.
Mum's the word: Mum here means silent (related to mumble or the mmm sound made with closed lips). It appeared in Shakespeare's Henry VI, Part 2 (Seal up your lips and give no words but mum.) and has been used since to mean keep quiet / say nothing.

Alternatives

Slang/Informal:

I ain't sayin' nuthin'. (Non-standard grammar for emphasis)
On the DL (Down Low meaning secret/private. Used more to *describe* secrecy than promise it, but implies keeping it quiet: Yeah, we gotta keep that on the DL.)
I'm zipped. / Zipped up.
Word. (Can sometimes mean I understand and agree [to keep quiet] in context)

Milder/Standard:

I'll keep that confidential.
I understand the need for discretion.

Vulgar/Emphatic (Expressing strong commitment):

I won't breathe a fucking word.
Wild horses couldn't drag it out of me. (Idiom, not vulgar, but emphatic)

Situational Appropriateness

Appropriate in informal and semi-formal contexts.
Mum's the word might sound slightly more quaint or dated to some, but is still understood.
My lips are sealed is very common.
In highly formal or legal situations, a more explicit confidentiality agreement would be used.

Misunderstanding Warnings

Generally very clear in meaning. The associated zipper gesture for My lips are sealed reinforces it.

Examples

Don't worry, I won't tell anyone about the surprise party. My lips are sealed.
Person A: Please don't tell anyone what I just told you. Person B: Consider it done. Mum's the word.
He asked me not to reveal the location, so my lips are sealed.

Dialogue

Chloe: I'm planning a surprise visit for my brother's birthday! Please don't mention it if you talk to him.

Mark: Don't worry, you can count on me. My lips are sealed.

Chloe: Thanks, Mark! It means a lot.

Mark: Mum's the word.

Response Patterns

Trust/Relief: Thank you, I appreciate it. / Okay, I trust you. / Phew, thanks.
Reinforcement: Seriously, not a soul!
Skepticism (if the speaker is known to gossip): Hmm, we'll see.

Common Follow-up Questions/Actions

After someone promises secrecy:

The person sharing the secret might reiterate the importance of silence: Really, please don't say anything.
They might express gratitude again.

The person who promised secrecy is expected to honor that promise and not discuss the information further.

Conversation Starter

No. It's a response to being entrusted with secret information.

Intonation

Often said in a reassuring, conspiratorial, or firm tone.
Can be slightly playful or very serious depending on the context.
Emphasis on sealed or Mum's. My lips are SEALED. / MUM'S the word.

Generation Differences

Both are well-understood across generations. Mum's the word might feel slightly older-fashioned.

Regional Variations

Both are common in major English-speaking regions.

Hang tight / Sit tight

🎲 Take five / Take ten

[1242] My lips are sealed