mind 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.

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.

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.