There are four theories often used to explain the phrase “mind your Ps and Qs.” All four of these theories are false.
- Children learning to write were reminded by their teachers to be wary of inadvertently reversing lowercase p’s into q’s, and vice versa.
- Back in the days when type was set by hand, printers could easily mistake lowercase p’s for q’s, hence the caution to be careful to not make that error.
- A tally of pints and quarts consumed was maintained on a chalkboard near the bar for each pub patron running a tab. Drinkers were advised to keep an eye on the count, lest the barkeep sneak a few extra marks onto it, thereby inflating the bill. Or, tipplers were to watch the count so as to not lose a sense of when it was time to call it a night and go home to their wives. Or, those working in the pub were admonished to be careful in marking the board lest they otherwise render the running tally inaccurate.
- That the p’s and q’s of the finger-wagging were “pleases” and “thank yous,” thus the saying had started out with the same meaning it now carries: “Mind your manners.