Complex sentence: The Connachta were a group of medieval Irish dynasties who claimed descent from the legendary High King Conn Cétchathach (Conn of the Hundred Battles).
Split into simpler sentences: The Connachta were a group of Irish dynasties who claimed descent from Conn Cétchathach. They took their collective name from their descent from Conn Cetchathach (Conn of the Hundred Battles).