While the pints & quarts issue is a cute, and charming story, I believe the origin to be in the type setting process for movable type printing before the invention of linotype. See: [[1]] [[2]] Johnparkw 20:24, 5 January 2007 (UTC)
There's no definitive answer. Each oriin seems as probable as the other. 66.167.147.162 02:14, 22 June 2007 (UTC)
I always thought this came from (or elluded to) 'pleases and thank-yous' and that this was something most often directed towards children (to teach them manners). Brits are still often heard using their P's and Q's ('please' and 'thank you', and later, 'pi** offs' 'fu** yous') proving P's and Q's are alive and well and still very much in use. Especially the latter variant... —Preceding unsigned comment added by 84.241.248.37 (talk) 12:26, 14 December 2007 (UTC)
Couldn't it be possible that it comes from the shortening of "Please and thankyous" to Ps and Qs? Neldo (talk) 00:59, 16 January 2008 (UTC)
Peace and Quiet
editA citation needs to come from a reputable source, not just a mention on a forum. I could claim, on the same forum, that Ps and Qs derived from Parsnips and Quinine and then add that to this article as a real theory. MrMarmite 07:56, 4 July 2007 (UTC)
Why not to join this article with http://en.wikipedia.org/wiki/Mind_your_p%27s_and_q%27s —Preceding unsigned comment added by 160.83.32.14 (talk) 14:14, 13 February 2008 (UTC)