The Romans invaded Briton in AD 43 but, in spite of many attempts, they never managed to subdue the tribes who lived in the north, the land the Romans called Caledonia. Eventually they gave up, and the peoples of the north continued with their own power struggles, largely undisturbed by Roman interference.
The first mention in a Roman document of the dominant tribes in the north was in the third century. The Romans called them Picti, which may have been a variant of the name they called themselves or possibly a Latin reference to how they tattooed themselves (picti is Latin for painted people).
By the turn of the tenth century, the Picts as a separate people had all but disappeared from the annals of history. In their place rose the Scots from Dal Riada.
What really happened that caused the fall of the Pictish kings during the ninth century is open to speculation, but one fact remains. In AD 843 or thereabouts Kenneth MacAlpin, king of the Scots from Dal Riada, became king of the Picts’ supreme kingdom, Fortriu, and eventually king of all Pictland.