Mind your ps and qs!

Factual Questions
#1

Perhaps this has already been discussed, but I’m wondering about the origin of the phrase “Mind your ps and qs.” I’ve heard it has something to do with typesetting, but I think this is not right. Am I wrong?

#2

It’s been discussed many times. Short answer is “origin unknown.” A few origins are suggested, all unproven, and most of them unlikely.
A few links:

http://www.word-detective.com/back-f.html

You can find literally thousands of sites saying the same thing.

#3

World Wide Words only comes up with “I dunno.”

#4

Cecil column

previous discussion including lots of (mostly discounted) hypotheses

#5

Thanks for the responses. I guess I’m at least as right as the next guy on this one!