From wikipedia, while not being a reliable source in general, I already know that Arabs came from the North from other sources:
> Arabs are first mentioned in Biblical and Assyrian texts of the ninth to fifth centuries BC where they appear as inhabiting part of Syria. Proto-Arabs are presumed to have originated from what is now modern-day northern Arabia, Jordan and southern Syria. Over time, Arabs spread further out sometimes replacing previously spoken Semitic languages.
> Arabs are first mentioned in Biblical and Assyrian texts of the ninth to fifth centuries BC where they appear as inhabiting part of Syria. Proto-Arabs are presumed to have originated from what is now modern-day northern Arabia, Jordan and southern Syria. Over time, Arabs spread further out sometimes replacing previously spoken Semitic languages.