splenetic

To vent one’s spleen is to express anger. There are healthy ways of doing this, of course, but vent too much of your spleen, or vent it too often, and you may be accused of being splenetic. Both spleen and splenetic trace back to the Latin word splen, which refers to the bodily organ responsible for storing and filtering blood, among other functions. So why the association with anger? In early Western physiology, a person's physical qualities and mental disposition were believed to be determined by the proportion of four bodily humors: blood, phlegm, yellow bile, and black bile. The last of these was believed to be secreted by the spleen, and to cause feelings and dispositions ranging from intense sadness (melancholia) to anger and violent temper—hence splenetic. In later years, the "melancholy" sense fell out of use (and the theory of the humors was discredited), but the "angry" sense of splenetic remains with us today.