Posted by Word Camel on August 13, 2002
I came across a nice reference in Peter Ackroyd's biography of London from Charles MacKay's volume of popular delusions and superstitions. Apparently in the early 17th century there were a number of wise women and wise men who would - for a price - examine your urine and predict your destiny, diagnose, ailments, etc. They were known as practitioners of "piss pot science.
I thought this might be one possible origin of the expression, 'piss pot' as a term of derision.