There is a teaching practiced by many protestants called sola scriptura. This is where only scripture (only books of scripture in the protestant main canon, ignoring the apocrypha) is allowed to contribute to doctrines that pertain to eternal life. It has a problem of being what is called self-referentially incoherent which is to say that it in itself does not come from scripture. However it is widely practiced such that many protestants will not accept doctrines important to eternal life unless they come from scriptures in their canon of scripture. Yet when it comes to understanding certain scriptures this causes a dead-lock because there are scriptures which cannot be understood correctly without sources outside the protestant canon. One example is the Nephilim of Genesis 6 and other books of Moses. Here is where you need to go outside of protestant canon books to find out who were the sons of God from whom descended the giants, the Nephilim. The Nephilim are also called sons of Anak or Anakim in canonised scripture of the Hebrew Bible. Understanding what that means requires a trip into Sumerian literature and the Book of Enoch. The Sumerians from whom Noah descended, and Noah’s own descendants, they were taught by Noah and Enoch to call the top angels “sons of God” or Anunnaki in their language. So when they were then told that the giants who terrorised the world centuries before the Flood were offspring of these Anunnaki the term sons of sons of God might have been coined and maybe the term “sons of Anak” or Anakim later used came into Hebrew from the Sumerian and Akkadian for sons of the Anunnaki (sons of sons of God).
