A person's character was thought to depend on the balance of the humours.

If they had too much blood, they would have a sanguine personality. This meant they would be red-faced and cheerful.

Too much plegm made a person phlegmatic, or heavy, slow and patient.

A melancholic person had an excess of black bile. This was supposed to make people greedy, cunning and cowardly. Too much might even cause leprosy!

Too much yellow bile was supposed to cause bad temper.

Even today, we still use the same words to describe peoples' characters.