,, Comorians are descendants of seafaring Bantu speakers from the East African coast, driven south by Oromo raiders
Oromo, the largest ethnolinguistic group of Ethiopia, constituting more than one-third of the population and speaking a language of the Cushitic branch of the Afro-Asiatic family. Originally confined to the southeast of the country, the Oromo migrated in waves of invasions in the 16th century CE
https://www.britannica.com/topic/Oromo
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around 1590 by a monk called Bahrey"The History of the Galla": "I have begun to write the history of the Galla in order to make known the number of their tribes, their readiness to kill people, and the brutality of their manners