Book argues that Classical Arabic and dialects may not be related

Source: OUP.

Arabic Indefinites, Interrogatives, and Negators: A Linguistic History of Western Dialects, traces the origins and development of the Arabic grammatical marker š/šī, which is found in interrogatives, negators, and indefinite determiners over a broad dialect area that stretches from the southern Levant to North Africa and includes dialects of Yemen and Oman.

David Wilmsen, a Professor of Arabic in the Department of Arabic and Near Eastern Languages at The American University of Beirut who has spent 30 years studying Arabic, and 20 years living in Jordan, Egypt, and Lebanon, challenges traditional assumptions about the origins of Arabic interrogatives and negators. He draws on data from old vernacular Arabic texts and from a variety of Arabic dialects to show that, contrary to much of the literature on the diachrony of this morpheme, š/šī does not derive from Arabic šay (شيء) 'thing'. 

Wilmsen argues instead that the usage dates back to a pre-Arabic stage of West Semitic and probably has its origins in a Semitic demonstrative pronoun. With this theory, Arabic šay could in fact derive from š/šī, and not vice versa.

The book demonstrates the significance of the Arabic dialects in understanding the history of Arabic and the Semitic languages, and claims that modern Arabic dialects could not have developed from Classical Arabic. 

The 264-page book is part of the Oxford Studies in Diachronic and Historical Linguistics series (ISBN 978-0-19-871812-3). It is available as a hardback and an e-book for £65. It will be of interest to historical linguists, particularly all those working on Arabic and other Semitic languages.