Mohandis in Arabic means Engineer, usually technical personnel are addressed this way. Even 'Mohallem' is quite respecteble form of addressing in Arabic. As for "Banyanis", I deduce there must have been plenty of Gujarathi/Rajasthani traders, some of the from 'Baniya' community. Was this a fact? Because I have heard there was (is) a sizeable north Indian community in Africa, and even Mohandas Gandhi wanted to try his luck in South Africa.
Regards Maurice
