Omar T. answered 12/06/20
Native Arabic Speaker with more than 20 years of teaching experience
I can not add much to the clear answers that my colleagues offered . However I can use different question that might make cast some light. What is the name of your رب. The one you worship. The answer is Allah اللة This name is unique and has no origin or derivatives in Arabic language as Mohamed M explained, while Allah has 99 more names derived from descriptions : The Great , The Wise , The Merciful , The One ..etc as Hebah S. also mentioned. رب in addition to meaning God has many other meanings.
May Allah enlighten us all and guide us on his path.