People used to use urine to tan animal skins, so families used to all pee in a pot & then once a day it was taken & Sold to the tannery.......if you had to do this to survive you were "Piss Poor".
But worse than that were the really poor folk who couldn't even afford to buy a pot......they "didn't have a pot to piss in" & were the lowest of the low.
I've heard my grandfather (b. 1911) and father (b. 1938) both say those 10,000 times.
Alteration for second was "don't have a pot to piss in
or a window to throw it out of..."
I've probably said both 1,000 times myself.
Interesting.
Had no clue of the derivation, but it does seem plausible in the colonial days.
My lineage is very much rural/agricultural. We had many tanneries in the area.
Now that I've read it on the internet, it must be true.......
EDIT/ADDITION - - as a youngster Environmental Health guy got a call for a nondescript vacant commercial 4-story building 400 yards from my office. Had gotten open/accessible to vermin and vagrants. Part of First floor was filled with salted cows' tails. 3 feet deep and 1,000's of them. Maybe 50-100 cubic yards worth (Think 2-5 big dump truck loads).
Machinery was gone, but surmised was a tannery many years before. May not have been correct.
I could only require the owner render it secure. Those tails weren't going to hurt anyone unless they wanted salty and aged Oxtail Soup......
While it was decades ago, it was late enough that the tails had salt on them, not urine......