Where Did the Saying “Mind Your P’s and Q’s” Come From?
When someone says, “Mind your P’s and Q’s,” it usually means “be careful of what you say or do.” There are many explanations of how this old expression may have originated.
One is that it is a warning to printers’ apprentices to be careful not to mix up the small letter “p” and the small letter “q” when setting their printing type.
A second explanation is that early-day alehouse keepers often chalked up customers’ debts on the wall. The number of pints the customer owed for were chalked under the letter “P,” and the number of quarts in the “Q” column.
Another explanation suggests that “Ps and Qs” is short for “please-s” and “thank-you-s”, the latter of which contains a sound similar to the pronunciation of the name of the letter “Q”.
This phrase would be used by parents to educate their children to not forget to use those polite words when they speak to people. Possibly, it meant “please” and “excuse me.” Young children would pronounce them as Ps and Qs.
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 from sailors in the 18th century who were reminded to pay attention to their peas (pea coat) and queues (pony tail).
Another possible and viable theory is after the Norman Invasion of 1066 the courts, church, and establishment were becoming French speaking and the English dialect of the 11th century had no qs; so one must watch their usage in court or discourse with the French Norman conquerors.
A possible origin or at least similar expression comes from 17th-century slang. “P and Q” meant “prime quality” or “highest quality”. It seems unlikely that the phrase “P and Q” stood for “prime quality”, because that does not explain the presence of the word and.
It is also possible that the expression refers to the careful reading of Medieval Latin texts: the letters “p” and “q” had various scribal 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.