Akkadian

baˀlīyu - (a synonym for lord, master) (CAD B 63)

As a synonym of bēlu “lord”, the present form must go back to WS *baˁl -. Following SAD 1 7, one has to assume that a nisbah suffix was attached to *baˁl -, even if this is rather unusual.

PS
*baˁl- - lord (Kogan 2015:396)