Posted by Lewis on October 30, 2003
In Reply to: Mind your p's and q's posted by sw on October 30, 2003
: I had thought that this phrase came from WWII. When the UK and US were planning D-day, Churchill was Mr. P and Roosevelt was Dr. Q in code speak. Obviously secrecy was of the utmost importance, so the people involved would always say 'Mind your p's and q's'. Had anyone else heard this? Or am I confusing phrases?
The most convincing origin of this is from printing - the letters that printers use are of course reversed, so lower case p and q are easily transposed. Inexperienced printers were told to mind their ps and qs accordingly. It became used to mean to behave with caution.
Another suggestion comes from serving ale - remembering to bill correctly for pints and quarts, but I for one am unsure that this is correct as the pint has long been the standard measure for beer and I cannot recall much serving of ale simultaneously in 1 pt and qt measures, even though quarts may have been served at one time.