mind your Ps and Qs

mind (one's) p's and q's

To be polite and well behaved; to mind one's manners. Be sure to mind your p's and q's when you visit your aunt this weekend! The mother reminded her young children to mind their p's and q's when they went over to their friends' houses for play dates.
See also: and, mind
Farlex Dictionary of Idioms.

mind your Ps and Qs

be careful to behave well and avoid giving offence.
Various suggestions have been made concerning the significance of P and Q . One obvious one is that a child learning to read or write might have difficulty in distinguishing between the two tailed letters p and q . Another is that printers had to be very careful not to confuse the two letters when setting type.
See also: and, mind, ps, Qs
Farlex Partner Idioms Dictionary
See also:
  • mind (one's) p's and q's
  • mind one's p's and q's
  • mind p's and q's
  • mind your p's and q's
  • ps
  • qs
  • come to mind
  • come/spring to mind
  • a mind is a terrible thing to waste
  • terrible
References in periodicals archive
I wrote recently about when to use apostrophes with single letters or runs of letters and detoured into one theory on the etymology of the phrase "mind your ps and qs."
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In the saying "Mind your Ps and Qs", what do P and Q stand for?
Quick Quiz
"They're a syndicate made up of ten barristers, so you had better mind your ps and qs or you could get a letter in post," said McBratney.
Rain fails to put dampener on the day for McBratney
Go back to school with a lesson in the traditional schoolroom but be careful you mind your Ps and Qs! Explore the underground coalmine and discover a miner's life in the 1850s.
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I had asked: "Where does the phrase mind your Ps and Qs come from?"
Your questions answered?
So, just tell him what you've told me that your mum is a bit of a dragon and you'll both have to mind your Ps and Qs, which includes not gobbling the food and keeping your mouths shut as much as possible.
Just Joan: Reader's letter
And finally, where does the phrase mind your Ps and Qs come from?
Your questione answered?