From raba'; a descendant of the fourth generation, i.e. Great great grandchild -- fourth.
see HEBREW raba'
H7256. ribbea
[רִבֵּעַ] adjective pertaining to the fourth (in a series); — plural in phrase וְעַלרִֿבֵּעִים עַלֹשִֿׁלֵּשִׁים i.e. those belonging to the 3rd and 4th Generations, Exodus 20:5 (E) = Deuteronomy 5:9; Exodus 34:17 (J), Numbers 14:18 (JE), compare 1 above