|Easton's Bible Dictionary|
Champion of El; man of God, a descendant of Cain (Genesis 4:18), so called, perhaps, to denote that even among the descendants of Cain God had not left himself without a witness.
Int. Standard Bible Encyclopedia
Methusael (1 Occurrence)
Genesis 4:18 And unto Enoch was born Irad: and Irad begat Mehujael: and Mehujael begat Methusael: and Methusael begat Lamech. (KJV WBS YLT)