Gen 6:2  The sons of God saw the daughters of men, that they
were good, and they took wives for themselves from all those
whom they chose. Gen 6:3  And YHWH said, My Spirit shall not
always strive with man; in their erring he is flesh. And his
days shall be a hundred and twenty years. Gen 6:4  The giants*
were in the earth in those days, and even afterwards when the
sons of God came in to the daughters of men, and they bore to
them; they were heroes which existed from ancient time, the men
of name.  נפל  /  נפיל nephîyl  /  nephil  From the root  BDB
Definition: 1) to fall, lie, be cast down, fail  The word naphal
is associated with miscarriages.  Translated as untimely births.
Job_3:16, Psa_58:8, Ecc_6:3  There are different ‘orders’ of
Nephilim.  Rephaim -raphah; a giant, dead, healers [Strong's
ref. 7497, 7496] Anakim – anaqiy; a desc. Of Anak, to choke,
necklace [Strong's ref. 6062, '60,59]  Emim – eymiym; terrors,
fright, horror, fear [Strong's ref. 367, '8]  Zuzim – zuziym; a
wild beast [Strong's ref.