Nephilim

The Nephilim, also known as Nephilites (; ) are mysterious beings mentioned in the Hebrew Bible―who are said to be large and strong. The word "Nephilim" is narrowly translated as "giants" in some Bibles but left untranslated in others. They are mentioned in the following books: Genesis, Numbers, and Ezekiel in the Hebrew Bible. The Nephilites and their identity are still unknown to this day.
Numbers 13:33 says that they later lived in Canaan when Israel conquered Canaan. A similar Hebrew term, read as "Nephilim" by some scholars, or as the word "fallen" by others, appears in the Biblical book Ezekiel 32:27
What are the Nephilim.
Some people think the Nephilim are giants that were created when fallen angels mated with humans, while others think they were famous ancient warriors and heroes that were created when the descendants of Seth wed the descendants of Cain. 
Brown-Driver-Briggs thought that the Nephilim were giants. Robert Baker Girdlestone thought that they are "the ones that caused the downfall." Donald Hendel thinks that it means "ones who have fallen."
The majority of ancient biblical translations think they were "giants." Symmachus thought they were "the violent ones," and Aquila thought they were either "the fallen ones" or "the ones falling [on their enemies]."
Some Jews believe that the Nephilim had children called Elioud. Aramaics think that Nephilim refers to the children of Orion. J. C. Greenfield thinks that the Nephilim is based on bad things in Sumerian beliefs. Early Arabs thought that fallen angels were sent to Earth looking like men, and they mated with humans.
Mentions of the Nephilim in the Hebrew Bible.
In Genesis 6:4:The Nephilim were in the earth in those days, and also after that, when the sons of God came in unto the daughters of men, and they bore children to them; the same were the mighty men that were of old, the men of renown.
In Numbers 13:32–33:And there we saw the Nephilim, the sons of Anak, who come of the Nephilim; and we were in our own sight as grasshoppers, and so we were in their sight.
In Ezekiel 32:27: They lie with the warriors, the Nephilim of old, who descended to Sheol with their weapons of war. They placed their swords beneath their heads and their shields upon their bones, for the terror of the warriors was upon the land of the living.
Idea about the Nephilim's fossils.
Cotton Mather thought that fossilized leg bones and teeth discovered near Albany, New York, in 1705, were the remains of Nephilim who died in a great flood, though paleontologists thought they were mastodon remains instead.