In ancient times before Christianity took over, the word “demon” had a positive meaning and had nothing to do with the devil or evil. Demon is an ancient Greek word (written ΔΑΙΜΩΝ in Greek) synonymous to the concepts of god, the divine and fate.
The ancient Greeks believed that a demon was a type of a spirit guide and protector similar to what we now know as guardian angels. They acted as an interface between god and humans. In many ancient Greek tragedies every hero has his own demon; what we refer to as fate. Demon was also used to describe various deities of Greek theology. A good example is that of twin brothers, Hypnos and Thanatos, the deities that personify sleep and death. The image featured in this article depicts Hypnos and Thanatos carrying the dead body of Sarpedon. Homer uses the word “demons” to refer to the gods of mount Olympus: ” He stayed his hand on the silver hilt of his sword, and thrust it back into the scabbard as Athena bade him. Then she went back to among the other gods (daimones), and to the house of aegis-bearing Zeus”.
With the advent of Christianity and its domination over the ancient Greek and Roman traditions the word “demon” seems to have been intentionally linked to evil.