Definition & Meaning of "[mind] {one's} p's and q's"

What is the origin of the idiom "mind one's p's and q's" and when to use it?

The idiom "mind one's p's and q's" has uncertain origins, but it is believed to have emerged in 17th-century England. It's a saying that emphasizes the need to pay close attention to one's manners, behavior, or words, especially in social or formal settings. The "p's" and "q's" in this context are often thought to represent particular letters, possibly in a printer's or typesetter's perspective, emphasizing the importance of being careful and precise.