Genesis 6:4

There were giants in the earth - נפלים nephilim , from נפל naphal , "he fell." Those who had apostatized or fallen from the true religion. The Septuagint translate the original word by γιγαντες , which literally signifies earth-born, and which we, following them, term giants, without having any reference to the meaning of the word, which we generally conceive to signify persons of enormous stature. But the word when properly understood makes a very just distinction between the sons of men and the sons of God; those were the nephilim, the fallen earth-born men, with the animal and devilish mind. These were the sons of God, who were born from above; children of the kingdom, because children of God. Hence we may suppose originated the different appellatives given to sinners and saints; the former were termed γιγαντες , earth-born, and the latter, ἁγιοι , i.e. saints, persons not of the earth, or separated from the earth.

The same became mighty men - men of renown - גברים gibborim , which we render mighty men, signifies properly conquerors, heroes, from גבר gabar , "he prevailed, was victorious." and השם אנשי anshey hashshem , "men of the name," ανθρωποι ονομαστοι , Septuagint; the same as we render men of renown, renominati , twice named, as the word implies, having one name which they derived from their fathers, and another which they acquired by their daring exploits and enterprises.

It may be necessary to remark here that our translators have rendered seven different Hebrew words by the one term giants, viz., nephilim , gibborim , enachim , rephaim , emim , and zamzummim ; by which appellatives are probably meant in general persons of great knowledge, piety, courage, wickedness, etc., and not men of enormous stature, as is generally conjectured.