One origin story of "mind your Ps and Qs" comes from English pubs and taverns of the seventeenth century. Bartenders would keep a watch on the alcohol consumption of the patrons; keeping an eye on the pints and quarts that were consumed. As a reminder to the patrons, the bartender would recommend they "mind their Ps and Qs."

A second origin story comes from early printing presses. Printers placed individual letters on a typeset to print a page of text. The letters were reversed, making it easy to mistake Ps and Qs in setting the type.

A reminder to stay watchful of the details could have come from this time as well. In a similar setting, this expression has been attributed as an adage for teaching children to spell. This second story has been disputed, however, as it can be just as confusing in typsetting or handwriting to confuse b and d.

Other origin stories, some considered "fanciful", could come from French instructions to mind one's pieds (feet) and queues (wigs) while dancing. However, there is no French translation for this expression. Another origin could be to sailors in the eighteenth century to pay attention to their pea (coats) and queue (wigs).

A possible origin or at least similar expression comes from seventeenth-century slang. "P and Q" meant "prime quality" or "highest quality." It has also been seen as "pee and kew," though it is unclear what either literally stand for. It seems also unlikely that this is the direct origin, for the common expression is not "mind your pq."

It is also possible that the expression refers to the careful reading of Medieval Latin texts: the letters 'p' and 'q' had various abbreviation symbols for different shortened words. For example, 'q' with a dot over it was the abbreviation for 'quod' while 'p' with a line through the tail of the letter was the symbol for 'per'. Minding that these abbreviations were interpreted accurately (i.e. that one read 'per' as opposed to 'post' or 'pro') would ensure the correct reading of the text.