splenetic
Bad-tempered, irritable, peevish, spiteful, habitually angry.
A sect, whose chief devotion lies / In odd perverse antipathies; / […] / More peevish, cross, and splenetick, / Than dog distract, or monkey sick.
Related to the spleen.
I have already described the general protuberance of the abdomen among the children throughout the Messaria and the Carpas districts, all of whom are more or less affected by splenetic diseases.
Where it comes from
The adjective form of spleen, borrowed from Late Latin spleneticus, from Latin splen. Anger was traditionally believed to originate from the fluids of the spleen.
Adapted from the Wiktionary entry splenetic (CC BY-SA 4.0).