From a good article on Haaretz:
“The Jews who lived in the regions of northern Iraq on the border with Turkey, Kurdistan and Azerbaijan brought a plethora of languages to Israel with them, some of which were classified as “Neo-Aramaic.”
The key to the development of these different languages was the isolation of the various Jewish communities in the region. Linguists explain that when an innovation is introduced in a language, it moves like a wave between the communities that speak that language. However, in mountainous areas, linguistic innovations cannot easily spread, and the more isolated the communities were – especially Jewish communities that kept to themselves – the more likely it was that a unique language would arise. “
-Steve