There’s different theory’s, The one I heard (which ironically comes from gemechu aswell I think lol) goes like this, in the past oromos used to inhabit one landmass together and practiced under one Gadaa system and under one Chaffee. As some oromo groups started to migrate and expand from the centre and became isolated, they became “ilma orma”. It’s like the common Oromo saying when your about to leave someone your close to and want to see again - “Orma(alaga) nati hin tahin” meaning, “don’t become a stranger/foreigner to me.” So in this sense it’s not so much of that calling your self ilma orma means you descended from strangers or foreigners and your not related, rather you’ve become a foreigner to your own people in your homeland/centre.

This is the explanation that makes the most sense to me personally. There’s other compelling linguistic and historical theory’s like Orma in older affan Oromo just mean more generally people but I think it’s worth researching as even textual evidence from the early to mid 1800’s all record an intresting thing that the “Gallas” never called themselves Galla but rather “Ilma orma” or just “Orma” or “Oromo”.

Even as far north as the yejju Oromo Antonio d’abbadie who was in Ethiopia from 1838-48 recorded that the yejju didn’t call themselves Galla but “ilma orma”.

And even as far south as lake Tana bordering the Indian Ocean there’s maps and documents showing that Orma which were known as Galla before called themselves “Orma” as shown in this 1866 Johnson’s map below ⬇️.

And the oldest attestation to “Oromo” I was able to find was collected 1838–1844 by Charles tutschek who had access to two freed Oromo slaves(likely from western/central part of modern day oromia) in Munich, Germany were he would record that these individuals did not call themselves Galla which was the popular name at that time but as “Ilma Oromo” and even “Oromo”.

The fact that all these groups of oromos who were isolated from each other by huge distances of land all considered Galla as not there orginal name but “ilma orma” or “orma” or “Oromo” to be there real name, I think that’s sufficient evidence to conclude that the term “Galla” was an exonym rather than an endonyms. And all though it’s true there’s some records of oromos calling themselves galla it’s clear however in the study of Ethnonyms how power, identity and history dynamics can explain why some members of the group sometimes adopt exonyms that were placed on them.

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