1. A po is a
chamberpot, a pot discreetly placed under one's bed for one's
personal needs when the night is
chilly and it's a long way downstairs and across the back garden to the
outhouse. No longer in common use, or at least the article of furniture isn't, so this
slang word sounds a bit dated.
I don't know where the word comes from: my guess is either a French pronunciation of pot -- either facetiously or from an actual equivalent pot de chambre --, or an abbreviation of some word like position as a euphemism for toilet. It might have given rise to the word po-faced.
In the node chamberpot, teleny gives an amusing example of one with Hitler's face on it and a punning inscription about another invasion of Po-land.
2. Po: Beyond Yes and No is a 1972 book by Edward de Bono, in which he explores the use of the concept PO as a way of avoiding a simple Yes/No dichotomy in one's thinking. He calls No the word of logic, since it helps rule out scientific hypotheses, and Yes the word of belief. His new tool PO is the word of creative thinking. It means something like "Let's back away from the position we're in and find other ways of looking at it".
De Bono says that outside mathematics no new thinking tools have been invented since the time of Aristotle, and the use of PO can be learned like any other skill. "Lateral thinking deals with the patterning of information not with the judgement of those patterns. Lateral thinking is prereason. PO is never a judgement device. PO is a construction device. PO is a patterning device. "
You can put PO in front of a sentence to begin thinking about it creatively. It is slightly reminiscent of the use of the Japanese word mu 'nothing' as an avoiding answer to problems.
Over the last two years I have had the reaction to the PO concept from forty thousand people. It has been fascinating to see how the reaction to PO differs from group to group. The division has been as follows:
Those who see the need for PO: poets, painters, sculptors, architects, designers, mathematicians, computer scientists, physicists, teachers (some), children, students, young people in general, journalists, photographers, bankers, business executives.
Those who don't: politicians, philosophers, lawyers, academics, teachers (some), and literary critics.
The division seems to be between those who are actually involved in doing something and producing new ideas and those who are too busy defending already established ideas to see the need for new ones. It is a division between those who are looking to the future and those who are looking to the past. That may be why young people have shown so much interest.
3. Po is the chemical symbol for polonium.
4. PO or P.O. is the abbreviation for post office, or perhaps postal order.
5. po. is the abbreviation/symbol for the old measure of length the pole, as in the notorious "rod, pole, or perch".