Someone on Quora linked to the Wikipedia article on the ‘Canaanite shift’:

In historical linguistics, the Canaanite shift is a sound change that took place in the Canaanite dialects, which belong to the Northwest Semitic branch of the Semitic languages family. This sound change caused Proto-NW-Semitic *ā (long a) to turn into ō (long o) in Proto- ( Read more... )