Oak leaves and acorns contain tanic acid used for tanning. The piss in the pot was old time way of tanning also, if you were really poor you did not have a pot to piss in for making your own clothes. I can't imagine the smell of people back then!
Remember the battle of Athens, TN!
"Work as if you were to live 100 Years, Pray as if you were to die To-morrow." --Benjamin Franklin