(2.) A Levite of the family of Jeduthun[?] (Neh. 11:17), also called Obadiah (1 Chr. 9:16).
From Easton's Bible Dictionary (1897)
... the square" is to add a constant (i.e., in this case, a quantity that does not depend on x) to the expression to the left of "=", that will make it a perfect square ...