Today I had a lot of fun with a group of mums and kids in a muddy obstacle race. I fell into the muddy pool while my mouth was opened and drank some muddy water by accident. Then I said to the other mum I better "keep my mouth shut" as I didn't want to drink anymore muddy water. The instructor then said I was rude by saying that.

Is it very rude and impolite to say that in that situation please?

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    You're a "mum" (mother), which makes you an adult, and you have to let some kind of "instructor" tell you what to say? Commented Aug 21, 2020 at 18:17
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    The instructor either simply misheard, or, is an idiot.
    – Fattie
    Commented Aug 21, 2020 at 19:11
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    You didn't need to end your question with "please". I'm guessing that this same instructor likely told you to do so for the sake of politeness? If so, this instructor may have some odd misconceptions about politeness.
    – Nat
    Commented Aug 22, 2020 at 4:15
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    I’m only mentioning this because it’s English Language Learners: “any more” should be two words. Commented Aug 22, 2020 at 9:48
  • @ChrisMelville In this case Commented Aug 23, 2020 at 18:48

4 Answers 4


The phrase keep your mouth shut could be used literally, as you have used it, to mean that you should physically close your mouth to keep something from getting into it. I can think of no situation where using the phrase as you have used it could be interpreted as you being rude.

The phrase can also be used to mean shut-up or don't speak. For example someone might say, "When we are in Mr. Bigg's office discussing big plans, you should keep your mouth shut." Used this way the phrase is stern at best and possibly rude.

Based on your experience it sounds like someone misinterpreted what you had said.

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    In the "Mr. Bigg's office" scene, it may be rude, but it might also be helpful. If Mr. Bigg has fired people in the past because they didn't keep their mouth shut, then telling someone in a rude way may be the best.
    – gnasher729
    Commented Aug 23, 2020 at 10:09

Answering from a US English perspective. I think what you said was misheard. I can't think of a situation where talking about keeping your own mouth shut would be rude. But telling someone else to keep their mouth shut would be considered rude.

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    Even when telling someone else to keep their mouth shut would not be impolite if the intention was to keep unwanted objects or substances from getting in, rather than words from getting out.
    – supercat
    Commented Aug 22, 2020 at 1:12
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    @supercat In the latter case, wouldn’t you keep your mouth closed? I’m no native speaker but “shut” sounds too connected to “shut up”. (Of course “keep my mouth shut” still seems unobjectionable). Commented Aug 22, 2020 at 9:47
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    @Blaisorblade Context is important here. Closed and shut are synonyms in this case (e.g. "Shut the door" or "Close the door"). Either usage is fine. Even telling someone they should "keep their mouth shut" may or may not be considered rude depending on context, familiarity with the person, and how it's said, but that doesn't apply to this question. Commented Aug 22, 2020 at 13:35
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    @Blaisorblade - it;s the other way around, "shut up" comes from keeping things, including mouths, shut.
    – Davor
    Commented Aug 23, 2020 at 15:57

Although I think the instructor may have misinterpreted, I can offer an alternative.

"keep one's mouth shut" usefully refers to speaking, especially when coupled with "keep".

I might have used the phrase "Next time I'll remember to keep my mouth closed!"

Or even safer, "Next time I'll remember not to leave my mouth open!"

  • I am ESL (or, honestly, ETL) so forgive me, but, seriously, who would, after falling, getting mud into one's mouth, say "Next time I'll remember to keep my mouth closed!"? Even if I omit the most obvious F-starting-sentence, the next F-starting option for an ETL would probably be ... desperately thinking ... "Fine ladies apparently use mud to treat their beautiful faces, so I had it a go"
    – Tuomo
    Commented Aug 22, 2020 at 15:48
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    It would be due to sarcasm. As a UK transplant in the USA I see British humor - in the form of sarcasm - as one of the most misunderstood parts of english language in england. A brit might take a mouth full of mud, spit out out and then say the above words while grinning. This is a cultural thing Commented Aug 23, 2020 at 8:22

I agree that the instructor probably misheard! But some context might be helpful.

"Keep your mouth shut" is a very rude, often aggressive or threatening way of telling someone to stop talking, or to not say anything (maybe about a particular subject). You could say it to a friend in a non-serious way, but you wouldn't say it to someone you were being polite to. If the instructor thought you said this to somebody, they definitely might criticise you for it!

"I'll keep my mouth shut" isn't about another person, so it's less confrontational - but it isn't exactly polite. It can be a bit like telling yourself to shut up, and some people might be sensitive to that kind of language. It can also imply that someone is ordering you to keep quiet - "I'll keep my mouth shut" can sound like someone is forcing that on you, or you've offended them, or you're implying there's something bad you're promising not to mention.

So I agree with the other posters who think they'd probably say "I'll keep my mouth closed" - it doesn't have any of that baggage or negative association. "Mouth closed" usually just means "not open", but "mouth shut" usually means "silent"

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    Also, in a group setting, because of group dynamics, it might seem that you're saying that "I'm keeping my mouth shut and so should you". To be fair, that was exactly the point! But it came out a little rude because "keep your mouth shut" is an idiom about shutting up.
    – nomen
    Commented Aug 24, 2020 at 17:14
  • I am puzzled why an "instructor" at an adult activity feels they have the right to police the speech of the people taking part. Commented Aug 24, 2020 at 19:49
  • It could be for any number of reasons, we don't know - but it's not strange that the person responsible for running an event with kids is trying to maintain standards of behaviour. You have to set a good example, you know? Commented Aug 24, 2020 at 20:10

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