Yes, but many tribes established in the 1600s or 1700s when Somalis were definitely Muslim still have those exotic old school Cushitic nicknames. So, it can't be all pre-Islamic.
Clans such as Geri, Yabrre, Gurgura, Marehan, Harti, Barsuug etc. were definitely not established in the 1600s as they took part in the Futuh Al Habasha wars. If they were able to field armies in the 16th century, they were definitely in existence hundreds of years before the 16th century, and so were other Somali clans. I believe the Somali ethnic group and clan system was probably formed in the first millennium.