Posted by Bruce Kahl on May 28, 2000
In Reply to: P's & Q's posted by James Briggs on May 28, 2000
These are some of the explanations I've seen advanced in various places:
Advice to a child learning its letters to be careful not to mix up the handwritten lower-case letters p and q.
Similar advice to a printer's apprentice, for whom the backward-facing metal type letters would be especially confusing.
An abbreviation of mind your please's and thank-you's.
Instructions from a French dancing master to be sure to perform the dance figures pieds and queues accurately.
An admonishment to seamen not to soil their navy pea-jackets with their tarred queues, that is, their pigtails.
There was once an expression P and Q, often written pee and kew, which was a seventeenth-century colloquial expression for "prime quality". This later became a dialect expression (the English Dialect Dictionary reports it in Victorian times from Shropshire and Herefordshire).
OED2 has a citation from Rowlands' Knave of Harts of 1612:
"Bring in a quart of Maligo, right true: And looke, you Rogue, that it be Pee and Kew."
Nobody is really sure what either P or Q stood for. To say they're the initials of "Prime Quality" seems to be folk etymology, because surely that would make "PQ" rather than "P and Q".