Was Somalia, and for that matter Djibouti, ever a part of Ethiopia? Were its people ever Christian?
It depends on who you ask, really. For those who subscribe to the idea of "Greater Somalia"
and pan-Somalianism, then the answer would most certainly have to be yes, because that would include a large chunk of Ethiopia proper which, while perhaps dominated by Somalis and other Muslim ethnic groups now, has always had and continues to have Christian people in it (Ethiopian author Nega Mezlekia, born in Jijiga in the Somali region, writes a little bit about this in his memoir, Notes from the Hyena's Belly
. Jijiga, the region's capital, is apparently 24% Amhara, the vast majority of which are Christian no matter where they reside).
If you're talking about Somali people as an ethnic group, then I'm not sure. I would guess not, but as Somalis are famous for their claim to be the world's only 100% Muslim ethnic group, I don't think that we'll ever really know if their pre-Islamic beliefs included any form of Christianity. Some people claim that particular Somali clans were originally Jews
. Somali historians generally admit to a kind of local henotheism called "Waaq" (named after the supreme god of that belief system). Interestingly, if you look this up on Wikipedia (under "Somali mythology"), even though the resulting page is clear that this was the Somali belief system before Islam, if you click through that page on "Waaq", it will lead you to a page that claims that Waaq was the pre-Islamic belief system of the Oromo people. The Oromo are not only not Somalis (though they do speak a closely related language), but they are concentrated primarily in Ethiopia and before the time of Ahmed Gragn were primarily Orthodox Christian
(they still have a significant Christian population today). I don't know if this is an attempt to whitewash the pre-Islamic history of the Somalis, or the Oromo, or what...