here is more info about the Scots being an Irish tribe....

The Romans left Britain never having conquered Scotland. When the Romans first arrived, there were nearly 20 Tribes, within 250 years there were FOUR main people.

The Picts ruled the north, east and most of central Scotland. Originally a coastal people, like so many of the early tribes, these early Celtic people left no written language, no records of their descendancy, which was through the female line. They were, in time, after mixing with other cultures, assimilated in with the new settlers and cultures. But in their height of power , the north and south Pictish culture was a rich and powerful one. Their Federated Kingdom, stretched from the Pictland hills to the Pentland Firth.

They left ornate symbol stones and advanced practices of art and culture as well as a formidable military.

The second of the four main groups left after the Romans, were the Britons or the Britons of Strathclyde. They would dominate the west of lower Scotland and some of England. Their lands stretched through Strathclyde south through Cumbria to Wales. This is most likely the Celtic people that helped settle Wales, or at the very least were strongly associated with the Welsh both in culture and language.

The third group, the Angles, from Germany settled southeast Scotland and portions of England. Warlike and hungry for land they drove out the Britons living near them, and carved out their kingdom.

Lastly, the fourth Tribe came to settle Scotland. They were also known as a warlike people, descended from Ireland. The origins of their name -- Scots is believed to be a corrupted form of Scottus or Scotti , which meant "raiders". A Celtic, warrior, combative and expansive race, the Scots came in about 500 A.D. Dalriada was the Kingdom of the Scots and stretched from east Ireland through the Western Isles to Argyll, in western Scotland.

Much of Scotland became Christian long before England. Due initially to a monk named Ninian or Saint Ninian. He was born around 350 A.D., a Briton, he went to the continent where he was ordained a priest, came back to Scotland and evangelized Galloway and the Southern Picts at Fife and Perthshire. Ninian's followers may have taken the new faith as far north as the Shetland Islands.
The Scots of Dalriada had Irish missionaries of their own. St. Oran probably established the first monastery at Iona. But St. Columba from Donegal, was the missionary who made the Scots a dominate Tribe. Legend has it that Columba came to Iona because of a copy he made of a psalter (holy book) without the owner's permission, and the man he borrowed it from took the law against Columba and won the case. So Columba, taking a vow, left for Scotland in exile. That is the legend, but most likely, it was simply Irish

Saint Columba arrived in Scotland, from Ireland, in about 563 A.D. with twelve followers. He was a skilled politician and helped the Scots, who owed allegiance to an Irish King, become independent from mainland Ireland, (Columba had Royal blood on both sides and this no doubt helped), by using his New Faith and Royal connections he helped the Scots to establish Argyll in western Scotland as an independent Kingdom.
The Irish Celtic Church was Monastic, unlike the great religious houses that were to come to Scotland in the middle ages. Strict, it demanded poverty and obediance from its clergy who were Monks, not Priests.

More at: http://members.aol.com/Skyewrites/origins2.html