Mind your P’s and Q’s is an old saying meaning “be on your best behavior” or “mind your manners.” It’s still used today, here and there. It’s the sort of thing a grandma might say to her grandchild. But calling it an “old saying” is an understatement, it turns out that it’s much older than you might think.
It first shows up in print as far back as 1602, when it meant to be at your best, or in top form: “Now thou art in thy Pee and Kue, thou hast such a villanous broad backe, that I warrant th’art able to beare away any mans iestes in England.” In that passage, “iestes” is probably “estes,” meaning “bounty” — in other words, whoever the author is talking about is in such good shape and so strong they could steal treasure from anybody. Not very good in the manners department.
By the mid 1700s, your P’s and Q’s needed constant minding, and the phrase seems to have meant being careful or deliberate.In 1825, the phrase was defined just the way it’s been used ever since: “‘Mind your p’s and q’s’, q.d. ‘be nicely observant of your language and behaviour’.” But it still had some other meanings; in 1876 another reference book defined it this way: “To be P and Q, to be of prime quality.”
The big question, of course, is where a weird phrase like that came from in the first place. Do the letters “p” and “q” really stand for something specific like “prime quality”? One theory is that it refers to the difficulty children have with “p” and “q” when learning the alphabet — and also the difficulty printers used to have when picking out lead type; the p and q are very similar and printers had to recognize them — and set them — in reverse. But it’s just as hard to distinguish “b” from “d”, and since you use those letters more often, it seems like that pair would make more sense. Besides that, the original meaning of the phrase doesn’t seem to have much to do with checking subtle differences.
Etymologists, undeterred (as usual) by far-fetched explanations, have also posited that
“P’s and Q’s” have to do with sailors, who in the 17th century might have been likely to have ‘pea coats’ and wear their hair in a braid, or ‘queue.’” This breaks new ground in the unlikely department. Aside from having nothing at all to do with how the phrase is used, “pea coats” were primarily issued in navies, where there were (often) rules about hair styles. So a pea coat and a queue would be unlikely to be things that a single individual would “mind” at the same time.
The explanations get even further out; if you’re learning to dance, and your teacher is French, you might learn steps called “pieds” and “queues.” Or if you’re tending bar, and keeping track of customers’ tabs on a slate or the like, you’d have to keep track of “Ps” (pints of ale ordered) and “Qs” (quarts of ale). It’s even been suggested that “p’s and q’s” somehow stands for “pleases and thank-you’s” — this is actually conceivable if you consider that if you say “thank you” quickly it can sound like “than-Q.” But these theories only apply to the more recent meaning of P’s and Q’s. Etymologists are going to have to do a lot more P and Q minding to figure out something that accounts for the real origin of the phrase, whatever it is.
