A "Poop jawn" is a combination of the Pennsylvania slang "poop" and "jawn". "Poop" orginated in Pittsburgh, likely due to the "poopy" nature of the city. "Jawn" on the otherhand was a product of Philadelphia, mostly as word that replaces the name of almost anything and everything. Thus, when used together, a "poop jawn" is anything that can be considered "poopy". Also, you can create a poop jawn straw man, meaning someone or something can embody the qualities of a "poop jawn" metaphorically.
by Napels January 28, 2015