In the early 1900s, factories that would tan animal hides would buy urine to use in the tanning process.  Arnold-DanielPoor families would all urinate in a large pot and at the end of the day take the kettle to the tanning factory and sell the urine. These people were referred to as "piss poor".  Believe it or not, some families could not even afford a pot to urinate in.  These people were so poor they "didn't have a pot to piss in".  Now you know.