From the Greek words melas (μέλας) meaning “black” and kholē (χολή) meaning “bile,” it was once believed that when one's spleen produced an excess of “black bile,” that person felt a particular sense of gloom. An ancient Greek school of medicine called “humorism” taught that body fluids (or “humors”) directly influenced a person’s mood. And so when the black bile was flowing, you felt melancholy.