"The Sons of God saw the daughters of men that they were fair; and they took them wives of all which they chose." - Genesis 6:2 "
Some commentators believe that the expression ‘sons of God’ refers to the ‘godly line’ of Seth , and ‘daughters of men’ to women from the line of Cain." - Commentary on the Living Bible "The Book of Giants was another literary work concerned with Enoch , widely read (after translation into the appropriate languages) in the Roman empire.
The ‘giants’ were believed to be the offspring of fallen angels (the Nephilim; also called Watchers) and human women."
Robert Eisman and Michael Wise, The Dead Sea Scrolls Uncovered (In The Book of Giants (i.e., 4Q531, 6Q8 Frag. 2 and 4Q530 Col. 2), "the name of one of the giants is Gilgamesh, the Babylonian hero and subject of a great epic written in the third millennium B.C.E."
The root of Nephilim is nephel which means: "untimely birth, abortion, miscarriage".
"The Nefilim were upon the Earth in those days and thereafter too. Those sons of the gods who cohabited with the daughters of the Adam, and they bore children into them. They were the Mighty Ones of Eternity, the People of the Shem." - Genesis 6:4 "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 unto them, the same became mighty men which were of old, men of renown." - Genesis 6:4 (King Jame’s version)
"Megalithic monuments, found by the Hebrews on their arrival in Canaan, will have encouraged legends about giants; as in Greece, where the monstrous man-eating Cyclopes were said by story-tellers ignorant of ramps, levers and other Mycenaean engineering devices, to have lifted single- handed the huge blocks of stone that form the walls of Tiryns, Mycenae and other ancient cities."
Robert Graves and Raphael Patai, Hebrew Myths: The Book of Genesis
On a parchment fragment 4Q201(En ara) copied ca. 200-150 B.C.E. found at Qumrum:
13. [They (the leaders) and all ... of them took for themselves] wives from all that they chose and [they began to cohabit with them and to defile themselves with them]; and to teach them sorcery and [spells and the cutting of roots; and to acquaint them with herbs.] And they become pregnant by them and bo[re (great) giants three thousand cubits high ...] - Book of Enoch (from Translation by J. C. Greenfield
"Later Jewish tradition has it that their seduction was at least partly their own fault since they had taught the girls the art of cosmetics, and so had begun the awful progress of mankind to degeneracy and sexual abandon. More important, ‘they taught them charms and enchantments, the cutting of roots, and make them acquainted with plants..." (Enoch 7:1ff)."
John M. Allegro, The Sacred Mushroom and the Cross "The Hebrew word for giants (nephilum) literally means the fallen-down-ones because these tall celestial beings fell from the sky. Their half-breed progeny and their descendants are often mentioned in the early books of the Old Testament until the last of them were finally killed off. They were known as the Rephaim [Hebrew for ‘phantoms’], Emim, Anakim, Horim, Avim, and Zamzummim. Some scholars speculate that this tradition of giants born from the union of gods and humans formed the basis for the demigod of Greek mythology."
"The Emim - a large and numerous people, as tall as the Anakim - had formerly inhabited it [Moab]. Like the Anakim, they are usually reckoned as Rephaim, though the Moabites call them Emim." "Now only King Og of Bashan was left of the remnant of the Rephaim. In fact his bed, an iron bed, can still be seen in Rabbah of the Ammonites. By the common cubit it is nine cubits long and four cubits wide." - Deuteronomy 2:11, 3:11
"Our skills and behavior are finely attuned to our size. We could not be twice as tall as we are, for the kinetic energy of a fall would then be 16 to 32 times as great, and our sheer weight (increased eightfold) would be more than our legs could support. Human giants of eight to nine feet have either died young or been crippled early by failure of joints and bones. At half our size, we could not wield a club with sufficient force to hunt large animals (for kinetic energy would decrease 16 to 32-fold); we could not impart sufficient momentum to spears and arrows; we could not cut or split wood with primitive tools or mine minerals with picks and chisels. Since these all were essential activities in our historical development, we must conclude that the path of our evolution could only have been followed by a creature very close to our size. I do not argue that we inhabit the best of all possible worlds, only that our size has limited our activities and, to a great extent, shaped our evolution."