Origin of Demons
The Nephilim
So what are demons? Demons are the disembodied spirits of the Nephilim who are mentioned in Genesis chapter six. The Nephilim are the offspring of fallen angels and humans. The Nephilim were destroyed in the flood, yet their spirits remained on the earth.
This view is the oldest belief among the Jewish people. It is a belief that the apostles held to as well. Let me prove why I believe this. http://tbm.org/origindemons.htm Origin of Demons