You realize that in ancient Judea they spoke Aramaic and that 500 or 600 years later in Arabia they spoke Arabic and were familiar with both Hebrew Scripture and the fledgling New Testament... you also must realize that these "Angels" are mythical beings without any real existence outside of the stories told about them.
Those desert tribesmen were surrounded for many centuries by powerful empires, each with it's own widespread religion, (not to mention their own religion) and each in turn dominating them in one way or another. Egypt, Persia, Greece, Rome, Assyria, Judea, Babylon. Sorry they're not in order and I think I missed a few.
OF COURSE Jibreel is Gabriel, who else could he be?