In the old days on the plains, cow patties were in great demand, since they made great fuel for the cold winter evenings. Tribes bartered and traded this form of manure. 

One day some new faces showed up and identified themselves as the Grood. The Grood must have been from the East coast, because they were not hip to the ways of the plains, as the locals found out one day. 

A couple of women were gathering fuel when one of the new guys showed up, placed some coins on the ground, gathered up a sackful of manure, loaded it on his horse and rode away. 

“That must be one of the new guys,” said one of the women. 

“How do you know?” asked the other.

“Easy, she replied,”Everyone knows that only the Grood buy dung.”