There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, and they bare children to them, the same became mighty men which were of old, men of renown.
There were giants in the earth in those days [Hebrew, ha-Nªpiliym (H5303)]. The Nephilim were in the earth in those days. The marked manner in which they are introduced to our notice is sufficient to prevent them from being identified with "the sons of God," or considered as the offspring of these; because they are described as already in existence and well known at the time when the Sethites began to intermarry with the other branches of the Adamic family. Who, or what, then, were the Nephilim? In the only other passage where the word occurs (Numbers 13:32-33) it clearly means giants, being derived, as Havernick suggests, from the mutually related roots of three verbs, yielding the fundamental idea of huge, extraordinary size. Nor can it be deemed incredible that in the antediluvian age, when, from the remains of quadrupeds and other inferior animals, we see that they were of an immensely larger type than the existing race of them exhibits, the physical powers and stature of Adam's descendants should have been greatly superior to the present standard of humanity. The analogy of nature would require that 'man among the mammoths' should, in physique, have borne some proportion to the magnitude of his bestial contemporaries.
Also, archaeology shows from the traditionary fables of the classical poets, as well as from the colossal monuments that are extant, that there were people in remote times of Cyclopean strength; and whether this may be predicated of mankind generally, or was the characteristic peculiarity of a certain class only, various circumstances contribute to warrant the conclusion, that in the world before the flood there were Titans distinguished by corporeal stature and energies far above the present scale. But although the idea of gigantic power does underlie the language of the sacred historian, the term Nephilim seems to bear a deeper significance; and if etymology may guide us, it describes a class of men of worthless and at the same time of violent character. It is commonly traced to naapal (H5307), to fall, and considered to signify either fallen ones, apostates, or falling upon others. In the first sense many of the fathers applied it to designate fallen angels. But it evidently describes a particular class of men, and hence, the latter meaning is preferable, intimating that the Nephilim were marauding nomads-men of a violent, overbearing, lawless character-who abused their bodily powers to obtain their selfish ends; who were constantly roving from place to place in quest of plunder, and, emerging suddenly from their retreat, made attacks both on the property and the lives of men (cf. Joshua 11:7; Job 1:15; Job 16:14; Job 22:15, where they are called mªteey ... 'aazew, associated in wickedness).
And also after that - afterward went in [Hebrew, yabo'uw (H935)]. The use of the future intimates the continuance of the relationship.
The same became mighty men which were of old, men of renown - literally, these were the heroes who from ancient times were men of renown [Hebrew, hagiboriym (H1368), mighty men: a term descriptive of any superiority, physical or mental, Genesis 10:9]. Robbers and tyrants who despoiled and oppressed the peaceful inhabitants were already existing in the world; and it was not at all wonderful that among the descendants of Cain numbers should be found addicted to deeds of rapine and bloodshed. Whether the Sethite husbands, having broken through the restraints of religion, settled in infidelity, or, slaves to female influence, they abandoned all care of their households to their worldly and godless partners, a progeny was reared under them, utter strangers to everything sacred and good, without either precept or example to control the outbursts of juvenile passions. Each succeeding race became worse. But the mixed marriages that became so frequent produced a vast increase of violent and lawless characters like the Nephilim-persons of reckless ferocity and audacious impiety, who spread devastation and carnage far and wide, and by the terror which their name inspired, obtained such lasting notoriety that in subsequent ages of ignorance and idolatry they were exalted by different nations, under various names, into the demigods of pagan mythology.