Now these are the generations of the sons of Noah, Ham, Shem, and Japheth. And the sons of Ham; Cush and Mizraim, and Phut and Canaan. And Cush begat Nimrod: he began to be a mighty one in the earth.
He was a mighty hunter before the Lord: wherefore it is said, Even as Nimrod the mighty hunter before the Lord.
Thus, from the tenth chapter of Genesis, Nimrod has come to be a nickname for anyone noted as a hunter.