Gen 6:4
Nephilim. The meaning of this term is uncertain. It occurs elsewhere in the OT only in Num. 13:33, where it denotes a group living in Canaan. If both passages refer to the same people, then the Israelite spies (Num. 13:33) are expressing their fears of the Canaanites by likening them to the ancient men of renown. Although in Hebrew Nepilim means “fallen ones,” the earliest Greek translators rendered it gigantes, “giants.” This idea may have been mistakenly deduced from Num. 13:33; one must be cautious about reading it back into the present passage. The Nephilim were mighty men or warriors and, as such, may well have contributed to the violence that filled the earth (see Gen. 6:13).
Num 13:33
Anakites are descended from the Nephilim (Gen. 6:4) and therefore must be quite invincible. (Given the exaggerated tone of the spies' account, their reference to Nephilim is most likely an expression of their fear and an excuse for their disobedience, rather than an accurate statement indicating that the Nephilim were still living after the flood.)
[From my ESV Study Bible footnotes]
3Mozzies