The Nephilim were added to the story of Noah to justify YHWH's destruction of the earth. I would contend they were not in the original text. The word is from the Chaldean word for the constellation of Orion which is Niphla which means "the mighty." In Hebrew lore one of the fallen angels Shemhazai hangs upside down in the constellation of Orion. This would connect the Nephilim to the constellation of Orion. My personal views and reasearch indicates Nimrod was represented by the constellation of Orion also and well as the violated Noah, and Herod of the NT. The violated or castrated Noah from the tent scene most likely was the original tale representing Orion. The rest were added due to syncretism.