[DubiousPusher]

Why is the person who treats most autoimmune diseases called a rheumatologist? Because the people who documented and categorized these diseases in Western medicine were believers in Humorism. That is a belief that human ailments stem from the imbalance of the four humors (blood, green bile, black bile and phlegm). They believed the inflammation in these disorders was the product of a phlegm imbalance, specifically of the mucus rheum. Hence the field name of Rheumatology.

The name dates back to the 17th century. My history is a little shaky, but as far as I can recall, the 17th century was before pharmaceuticals, pesticides and the entire industrial revolution. But maybe I need to get on that Gary Kasperov history where the Roman Empire fell in like 1940 or whatever.