What is the origin of the phrase, "mind your P's and Q's?

Answer 1

In the days when they had the old type printing press and had a man that set the letters of the alphabet in order to run off the newspaper.

Because, the letters p's and q's look much alike and the press setter occasionally miss took the q for the p, the owner would commonly tell the type setter to mind his p's and q's.

Thanks for the question.

Answer 2

came from england,the pub keeper sold ale in pints and quarts,some owners started cutting there pints&quarts about 1/5 of the normal,when towns people found out who were doing this,they would warn patrons as they went in ,to watch there pints &quarts,mind your ps&qs is just a way of saying.these people will steal from you