We know almost nothing about the Nephilim. Who were these people?
The word “Nephilim” is the Hebrew word spelled with English letters that sound similar.
The translators of the Septuagint used the Greek word for “giants” to translate the Hebrew term nepilîm.
There are several reasons for their decision.
The ten scouts called the large-sized Canaanites “Nephilim” (Num. 13.33); they were described as “heroes of old, persons of name,” which could give them a legendary sort of stature; and, again, perhaps their fathers were angelic and so they could be physically large.
Neither of the first two reasons are adequate.
The spies were fabricating a myth in Numbers 13.33, and “heroes of old, persons of name” does not need to be related to physical stature.
The third line of reasoning is a hypothesis built on top of another hypothesis, thus it is weak. Even if the Nephilim were the “biological” offspring of “angelic men” and human women, there is no way to know whether this would affect their physical stature.
The Hebrew word for Nephilim probably means something like “fallen ones.” In my view, translating it as “fallen ones,” whoever or whatever they were, captures the spirit of the passage.
The fallen ones are the angels that were cast out by the Almighty for their jealousy of humans and their failed rebellion. They were banished to earth until judgement day. The watchers were already here on earth as guides to humans in the beginning. They were banished here also because they violated the prime directive to put it simply. They mingled with humans and taught them things they weren't ready to learn.
The nephilim were the offspring of the sons of God and the daughters of man. Now, I heard this explained as the people who worshipped God mated with the people who didn't...imo I believe this isn't accurate. I think it was the fallen ones and/or the watchers who mated with humans, who's offspring were the heroes of old. One example would be Heracles being the son of a god and a mortal.
And yes I believe it affected their physical stature. That's just simple DNA. If you think about it, a person only has to be like 7+ ft. tall to be considered a giant, Goliath was like 9 ft I believe. And that's if you're taking that description of giants literally and not figuratively.