Atrabilious

1 : given to or marked by melancholy : gloomy
*2 : ill-natured, peevish

"Atrabilious" is a somewhat rare word with a history that parallels that of the more common "melancholy." Representing one of the four bodily humors, from which it was once believed that human emotions originated, "atrabilious" derives from the Latin "atra bilis," literally meaning "black bile." The word "melancholy" derives from the Greek "melan-" and "chole," which also translates as "black bile." In its original sense, "atrabilious" meant "melancholy," but now it is more frequently used to describe someone with an irritable or unfriendly temperament. A word with a meaning similar to that of "atrabilious" is "splenetic," which is named after the organ in the body (the spleen) once thought to secrete black bile.