Trash fills are old traditions.
 
At Hen Domen [a 12th century Norman motte and bailey castle in
Montgomery, Wales] there were few artifacts within the foundation
lines of buildings within the ditch and palisade. The site seemed
picked clean except for a wood and clay lined trash pit that was
absolutely filled with alot of material including pieces of intact
leather from a pair of boots. Nobody could explain why a medieval
settlement should maintain such levels of cleanliness.