Nephilim
The Nephilim [Heb. “those who fell” or “those who were cast down,” from the Semitic root naphal “to fall”) are a biblical race of giants or demigods, referred to in Genesis 6:4. The Greek Septuagint, a late translation of the Hebrew Scriptures, rendered the word Nephilim as “giants.” (“There were giants in the earth in those days...”) Zecharia Sitchin concludes from his study of ancient Sumerian texts that the Nephilim were an extraterrestrial race who “fell” to earth (landed) in spacecraft 450,000 years ago.
The term is also used to describe the fallen angels who were cast out of heaven into the earth (Rev. 12:7–9).
For more information
Elizabeth Clare Prophet, Fallen Angels and the Origins of Evil
Zecharia Sitchin, The Twelfth Planet (New York: Avon Books, 1976)
Sources
Jesus and Kuthumi, Corona Class Lessons: For Those Who Would Teach Men the Way
Elizabeth Clare Prophet, Fallen Angels and the Origins of Evil