I enjoyed the video.
Scotland and Ireland have had people settled in them since the Palaeolithic period, over 12,000 years ago. The first people were neanderthals and homosapien crosses called the Partholans. Their population crashed during the Ice Age. Around 8000BC, more people moved into Ireland and Scotland, who knew agriculture and intermarried becoming the Nemedians. Later, more people moved in from Iran, pushed out by the Scythians. They became the Firbolgs. Around 3000BC Celts from Spain moved in intermarried with the Firbolgs and became the Tuatha Dé Danann which are the people now often called Fairies. They had a fair amount of nonhomosapien DNA.
Around 2000BC the Milesians came to Ireland. They were Celts, originally from Spain, who had been living abroad as mercenaries, in most recently Egypt. They were led by two brothers, Heremon and Heber. Their father was Milesius of Spain and their mother was the daughter of an Egyptian Pharaoh, though some say Moses was her father. Her name was Scota and Scotland is named for her. The first Milesians settled in Ireland. The next wave of Milesians to arrive was given land in Scotland. The Milesians killed off most of the Tuatha De Danann men and took their women as wives.
The remaining, mixed species, Tuatha De Danann people, as the displaced peoples before them did, hid out in the old Neolithic and Palaeolithic monuments and forts giving rise to the fairy mythology.
The Milesian royalty traded later born princes and princesses with Norway, Denmark and Sweden and Ireland and Scotland were heavily settled by Vikings, like the rest of Britain.
The so called Black Irish are of mostly Celtic origin without the Viking genetics. Scots from the nonroyal lines have less Viking influence and more Celtic and Welsh DNA.
Keith