Starting at least in the 10th century, African holy men who had converted to Islam and learned Arabic began to modify Arabic writing to enable them to spread the religion more easily. The resulting Ajami script - the name comes from the Arabic word for stranger - helped make Islam accessible to shepherds and other commoners who could not understand Arabic.
But officially speaking, it has also been widely ignored. Uncounted Ajami manuscripts squirreled away across the continent have gone untranslated, even unseen, by scholars. Even in African countries where it is still used, the script lacks government recognition. In French colonial archives from Africa, Ngom says, Ajami documents remain classified as “unreadable Arabic” - based on the mistaken notion that writing in African languages simply did not exist.
via the Archives Listserv