The name Nephilim in the Bible
The Nephilim are mysterious supermen from ancient times, men of name, who lived before and after the flood of Noah. Before the flood they are mentioned in Genesis 6:4, and after in Numbers 13:33. The question this raises is: who are the Nephilim and how did they survive the flood? If Noah, his sons or any of their wives had been Nephilim, the text would have certainly mentioned it, and the Nephilim would have been treated more positively.
Genesis 6 tells us that the Nephilim were fathered by 'sons of Elohim' with human females. The phrase 'sons of God' may indicate angelic creatures but also the members of some very strong race. It seems that Nephilim were generated from human stock, not just once but often and separately, and not only before the flood but also after. The Bible basically states that biology allows that human females may be and have indeed been impregnated by spirit beings, a fact of course made ultimately evident in the conception of Jesus Christ.
The Nephilim seem to be divided into several sub-categories. The spies who were sent to Canaan reported seeing children of Anak, or the Anakim, who were Nephilim (Numbers 13:33). The word for children that is used in Numbers 13:28 is ילד (yalad) and means 'born ones,' that means of regular birth and not of some 'son of Elohim.' The name of the father of Anak is Arba, and his city, Hebron, is given to Caleb (Joshua 15:13). Caleb subsequently drives out the three sons (perhaps again three subdivisions of the Anakim) of Anak, whose names are Sheshai, Ahiman and Talmai. Strangely enough, in 1 Chronicles 9:17 occurs a small list of Levites whose names are: Akkub, Ahiman, Shallum and Talmon. This curious symmetry remains unexplained.
Deuteronomy 2:10 speaks of Emim, a people as great, numerous and tall as the Anakim. Deuteronomy counts both the Anakim (who are Nephilim) and the Emim among the so-called Rephaim, but in Genesis 14:5 the Rephaim and the Emim are listed separate. Genesis 14:5 also lists the Zuzim, which many (possibly erroneously) suppose are the same as the Zamzummim of Deuteronomy 2:20, who are a people like the Anakim and also counted among Rephaim.
Etymology and meaning of the name Nephilim
It is not clear where the name Nephilim comes from. There are a few possibilities, and scholars argue about the likelihood of each of them. First of all, the word nephilim is a plural and the single form, נפל (npl), does not occur in the Bible (which by itself is not at all unusual). In another context, however, the word נפל (nepel), which is spelled identical but pronounced slightly different, means untimely birth or abortion. It comes from the verb נפל (napal), to fall or be cast down:
HAW Theological Wordbook of the Old Testament mentions the above similarity with some disdain and pronounces a much more likely etymology based on words such as פלא (pala), to be marvelous, wonderful, or פלה (pala), to be distinct, marked out, or even פלל (palal), to intervene, interpose, pray. This latter verb is one of many for prayer and other interventions, and in search of origins of this particular verb some scholars end up right back at נפל (napal), to fall (i.e. to prostrate oneself). This becomes especially compelling when we remember that the name Rephaim has to do with a verb that means to sink, let drop, fall slack.
The Nephilim are the Fallen Ones, and the Marvelous Ones.
BDB Theological Dictionary adds a very interesting note, although, in its signature grumpy style, pronounces any etymology 'dubious' and 'precarious': The words for Nephilim, נפילים and נפלים bear a striking resemblance to Nephila, the Aramaic word for Orion: ניפלא and נפילא.
Ergo: the Nephilim are also the Orionids.