mind one's p's and q's, to

Prov. to behave properly; to display good manners. When you children go to visit Aunt Muriel, you'll have to mind your p's and q's; not like at home, where I let you do as you please. We'd better mind our p's and q's for this new teacher; I hear he's very strict.

Practice good manners, be precise and careful in one's behavior and speech, as in Their grandmother often told the children to mind their p's and q's. The origin of this expression, first recorded in 1779, is disputed. Among the more interesting theories advanced is that bartenders kept track of customers' consumption in terms of pints (p's) and quarts (q's) and the phrase referred to an honest accounting; that schoolchildren were taught to be careful in distinguishing the letters p and q; and that French dancing masters cautioned pupils about the correct performance of the figures pieds and queues (either abbreviated or mispronounced in English as p's and q's).

If you mind your p's and q's or watch your p's and q's, you try to speak and behave politely. She always minded her p's and q's in front of the queen, but their relationship wasn't that close. Note: This expression may originally have been a warning to children not to confuse p's and q's when learning the alphabet. Alternatively, `p's and q's' may stand for `pleases and thankyous', or expressions of politeness.

To be very particular about one’s words and/or behavior. The original meaning of p and q has been lost, and there are various theories, ranging from “pints and quarts” in the bartender’s accounts, to children confusing the two letters in learning their alphabet, to the French dancing master’s pieds and queues, figures that must be accurately performed. The term was used from the seventeenth century on but is heard less often today.

Behave yourself. Opinion is divided over what the letters in the admonition to “mind your p's and q's” mean. They might have been two similar-looking letters that typesetters were warned not to confuse. They might have stood for pints and quarts that tavern keepers could have confused. Neither, however, is close to the idea of being on your best behavior, but p standing for “please” and q for “thank you” (pronounced thank-kew) does. And that's how generations of parents reminded their children to remember their manners.