There were a lot of Somalis who settled in the Ethiopian Highlands before and after the conquest of Abyssinia. I may drop some stuff Iβve been keeping in the backburner if this is all true.
When Imam Ahmad ibn Ibrahim al-Ghazi conquered Abyssinia and was consolidating his control over the newly acquired Abyssinian territories, he did so by appointing Muslim governors over districts and provinces to administer the lands under the Sultanate.
The conquered Habesha would become farming peasants to their Muslim lords and knights and pay annual Jizya taxes. The Muslim governors who settled in the provinces would build their residences and mosques for the arriving Muslim families from the lowlands and new converts. Every knight who fought in the conquest was granted land in Abyssinia.
This settler policy can be traced back to Sultan Badlay who reconquered the Bali province from Abyssinia and settled over a thousand Muslim families in the region and appointed his brother Khair al-Din as governor who ruled from a city named Rakla.
Many tribes in Ethiopia claim Somali descent from these conquerors, these settled Somalis would mix with the diverse local populations and have descendants that would carry their lineage. Ulrich Braukamper who did research in the early 2000s in Ethiopia wrote about how the Somali would stay in the conquered territories of Hadiya, Bale, and Gurage mountains as settlers and still be identifiable by clan names such as the Habr Yunus, later bastardized to Habarnoosa by the Oromos, who live near Lake Zway, south of modern-day Addis Ababa, or by their cities of origin such as BΓ€rbΓ€re who live in the Gurage Mountains and claim descent from Somali settlers who originated in the coastal city of Berbera. Without a doubt more existed in the Highlands but they most likely wouldβve assimilated or have been forcefully converted to Christianity
Also in the 1800s, Somali Issas lived near Laibela, weβve had a deep presence in the Abyssinian highlands.