what does P's & Q's mean?...what are the initionals for p and q?

Question

when someone says"they're on their P's & Q's in that classroom"....the classroom be quiet as i don't know what.

Answer 1

It means "Be on your best behaviour; be careful of your language" and stands for minding your pints and quarts, or so most resources say:

"Mind your pints and quarts. This is suggested as deriving from the practise of chalking up a tally of drinks in English pubs (on the slate). Publicans had to make sure to mark up the quart drinks as distinct from the pint drinks. This explanation is widely repeated but there's little to support it, apart from the fact that pint and quart begin with p and q."

But these people offer alternative hypotheses: http://www.phrases.org.uk/meanings/248000.html

- Advice to printer’s apprentices to avoid confusing the backward-facing metal type lowercase Ps and Qs. I've never heard any suggestion that printer should mind their ds and bs though, even though that has the benefit of rhyming, which would have made it a more attractive slogan.

- Mind your pea (jacket) and queue (wig). Pea jackets were short, rough woollen overcoats, commonly worn by sailors in the 18th century. Perruques were full wigs worn by fashionable gentlemen. It is difficult to imagine the need for an expression to warn people to avoid confusing them.

- Mind your pieds (feet) and queues (wigs). This is suggested to have been an instruction given by French dancing masters to their charges. This has the benefit of placing the perruque in the right context - so long as we accept the phrase as being originally French. There's no reason to suppose it is from France and no version of the phrase exists in French.

- It is advice to children learning to write to take care not to mix up the lower-case letters p and q. Again, the 'd' and 'b' counter argument applies.

- It derived as reminder to children to be polite. This is supposed to be as a form of 'mind your pleases and thank-yous' - 'mind you pleases and kyous'. Pretty far-fetched that one.

- P and q stands for "prime quality." There is, or rather was as this now seems to have also been withdrawn, a 1612 citation which links PQ with 'prime quality'. If that's the origin why isn't the phrase mind your PQ?

Answer 2

To mind one's Ps and Qs is an English phrase meaning to mind one's manners. There are numerous theories about the origin of the phrase. One is that it began in British pubs as an abbreviation for "mind your pints and quarts." Supposedly, this warned the bartender to serve full measure, mark the customer's tab accurately, etc. Alternatively, it could be a warning to customers that they are misbehaving due to being drunk (from having too many "pints and quarts"), or even a way of telling the bartender to mind his own business (as in mind his drinks, rather than the customers).

Another suggestion is that the phrase originated in the printing trade, at the time when printing presses used movable type set by hand. When looking at the type, all the letters are in mirror image so that they will print on paper correctly. Because the letters "p" and "q" look very similar and were stored side by side in the type cases, it was easy for a typesetter to pull a letter from the wrong slot and not notice this. When the type was removed from the press and sorted back into the type cases, mixing q's with p's was likely unless care was taken. A similar theory tells of a teacher instructing a young student to write p's and q's appropriately, as they look similar.

Still another theory hypothesizes that the term might be in some way connected to the phrase "peace and quiet."