There are a number of theories as to the origin of the phrase 'Mind your p's and q's'. My favourites is to do with being mindful of how much alcohol one was consuming in taverns a long time back. Pints and quarts being p's and q's.
Also having read through this thread it's a fact that Groucho would be a good man to have on a pub quiz team.
Also having read through this thread it's a fact that Groucho would be a good man to have on a pub quiz team.