Where does “Rabb” come from?

Rabb is an English word from Anglo-Norman Robert, ultimately derived from a Germanic name of uncertain origin and meaning.

Ancestry of “Rabb”, step by step

Step	Language	Word	Meaning
1	Arabic	رَبّ	lord, master; God; Lord; Lord
2	Proto-Semitic	rabb-	to expand, to extend; lord, owner, chief;...

Rabb — Etymology, Origin & Word History | Etymology Explorer