Moreover, we have in these mighty men, the "men of renown," the explanation of the origin of the Greek mythology. That mythology was no mere invention of the human brain, but it grew out of the traditions, and memories, and legends of the doings of that mighty race of beings; and was gradually evolved out of the "heroes" of Gen. 6:4. The fact that they were supernatural in their origin formed an easy step to their being regarded as the demi-gods of the Greeks.
Tell ya frankly, I haven't the faintest idea.
Your question does seem to be in line with what Bullinger is saying here though.
I believe the Nephilim were the Titans of Greek mythology.