Nephilim is a plural word that is used elsewhere only in Numbers 13.33, where the spies sent out by Moses compare themselves as grasshoppers to the Nephilim, often translated in that text as “giants.” If they were literally “giants,” it is fair to ask why Caleb and Joshua were nevertheless convinced that the Israelites could conquer the land. The fact that the term nefilim was known and used in Moses’ time does not necessarily mean that these kinds of men survived the flood. It can mean that just the name and the concept survived. There is no doubt that Middle Eastern mythology knew about giants, and that belief in the existence of such men was common at the time of the writing of Genesis.
There have been many guesses made to explain the history of the word Nephilim, but none has any real likelihood of being true.
Those who understand the sons of God in verse 2 as human beings and not supernatural beings, reject any reference to the Nephilim as offspring of human and heavenly unions, and so the Nephilim are taken to be powerful and violent men who existed along with those men who carried the title of “sons of God.” Luther for instance interpreted the Nephilim not as giants but as tyrants who fell upon the people and treated them violently.
Modern translations divide into two groups in the way they handle Nephilim: (1) those like Good News Translation, Biblia Dios Habla Hoy, Die Bibel im heutigen Deutsch, Bible en français courant, and Traduction oecuménique de la Bible, which translate “giants,” as did the Septuagint; (2) Revised Standard Version, New International Version, Revised English Bible, New Jerusalem Bible, New Jerusalem Bible, which transliterate Nephilim. Some provide a cross reference to Num 13.33, and some that have Nephilim in the text say “giants” in a footnote. Moffatt compromises with “Nephilim giants.”
If the word Nephilim is retained in translation, it will have little or no meaning; and if it is used it will have to be explained either in the text or in a note. If a word for giants is not known, it may be possible to say, for example, “huge and powerful men,” or it may be possible to compare these men with some local object such a “men as big as trees.” As well as “very tall men,” there are other expressions in existing translations, such as “very big men with double strength” and “unbelievably big strong men.”
Were on the earth means lived on the earth, existed in the world.
In those days: days is used idiomatically in Hebrew as well as in English with the sense of “at that time,” “during that period,” “back then.” And also afterward has been objected to by some scholars as not fitting into the structure of the sentence. However, there is no good reason for removing it. Also afterward is more clearly expressed by Good News Translation as “and even later.”
Sons of God repeats the expression from verse 2 as being the fathers or ancestors of the mighty men in this verse. Came in to is an indirect way of saying “had sexual relations with.” The expression probably refers to visiting or coming into the area of the house where the woman sleeps. See comments on “took to wife” in Gen 6.2. The result of the sexual union is that the daughters of men, that is, the human women, gave birth to their children.
These were the mighty men: These refers to the “Nephilim” who are now called mighty men, a term that in Hebrew refers to valiant, courageous men. They were men who were warriors and famous in popular stories for their heroic exploits. Good News Translation calls them “great heroes.” These “heroes” were of old, that is, they lived in ancient times, a long time ago. They are further described as men of renown, which is literally “men of name.” The idea is that their names were known by everyone; they were famous, very important men. Translators should avoid giving the impression that these men are bad or socially rejected.
In translating mighty men or “heroes,” some translations focus particularly on the “warrior” feature and have expressions such as “fearsome fighters”; others focus more generally on “power” or “strength” in expressions like “very strong to do all kinds of work.” A number of languages have terms like the English “hero” for men who are powerful in real life or in story. For men of renown many languages are able to use idiomatic expressions like the Hebrew, such as “men who have a [big] name” or “men whose names were in every mouth.” Other languages use qualifying words like “famous men.”
Quoted with permission from Reyburn, William D. and Fry, Euan McG. A Handbook on Genesis. (UBS Helps for Translators). New York: UBS, 1997. For this and other handbooks for translators see here .