A cacodemon is an evil spirit or a demon. The opposite of a cacodemon is an agathodaemon or eudaemon, a good spirit or angel. The word cacodemon comes through Latin from the Ancient Greek κακοδαίμων kakodaimōn, meaning an "evil spirit", whereas daimon would be a neutral spirit in Greek.

Why is it called Cacodemon?

The word cacodemon comes through Latin from the Ancient Greek κακοδαίμων kakodaimōn, meaning an "evil spirit", whereas daimon would be a neutral spirit in Greek. It is believed to be capable of shapeshifting. ... In astrology, the 12th house was once called the Cacodemon for its association with evil.

What is the Cacodemon based on?

The Cacodemons appear in all Doom games and actually are based on the Greek word, κακοδαίμων, which means malevolent spirit.