Phlegm and the Four Temperaments

According to the ancient Greeks, human personalities were controlled by four bodily fluids or semifluids called humors: blood, black bile, yellow bile, and phlegm. Each humor was associated with one of the four basic elements: air, earth, fire, and water. Phlegm was paired with water—the cold, moist element—and it was believed to impart the cool, calm, unemotional personality we now call the "phlegmatic type." That's a bit odd, given that the term derives from the Greek phlegma, which literally means "flame," perhaps a reflection of the inflammation that colds and flus often bring.