Wikipedia:

Anselan O Kyan, who was a son of one of the Kings of Ulster, landed on the northern coast of Argyllshire, near the Lennox, about the year 1016. Assisting Malcolm II of Scotland in repelling his old enemies the Danes, on two different occasions. Upon their arrival in Scotland, he received a grant of land in the north of Scotland, East of Loch Lomand. The beginning of the Buchanan clan can be traced back to him.

Succession of Clan Buchanan Chiefs

The first six Clan Chiefs are poorly represented in historical records and are included by some Clan historians and omitted by others. Buchanan of Auchmar and Guthrie Smith commence their respective numbering of Chiefs at a different person, and describe a different order and number of Chiefs following Sir Walter 11th of Buchanan. In part this is due to the heir apparent not succeeding to the chiefship before he dies and chiefship passing directly from grandfather to grandchild. The following lineage reconciles Guthrie Smith and Buchanan of Auchmar and their respective numbering is in parenthesis.

• 1st – Anselan O'Kyan,[62][63] son of a petty king from Ulster, Ireland, in the service of Malcolm II of Scotland from whom he received a grant of land in Lennox. He married an heiress of Denniestoun and by her had a son, John.
• 2nd – John,[64] whose son and successor was Anselan.
• 3rd – Anselan,[65] whose son and successor was Walter.
• 4th – Walter,[65] whose son and successor was Girald.
• 5th – Girald also called Bernard,[65] whose son and successor was McBeath.
• 6th – McBeath (MacBethe/McBeth) McCausland,[65] whose son and successor was Anselan. http://en.wikipedia.org/wiki/Clan_Buchanan

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McCausland (surname)

McCausland (Mac Ausaláin in Gaelic), meaning "Son of Absolom" is a surname of Irish and Scotch-Irish origin. The family came from Ireland to the Loch Lomond region of Scotland sometime before the twelfth century. They are said to have settled through a charter on the island called Clarines - Clarich, in Loch Lomond. In one version of how the surname came to be, the name is reputed to come originally from Absalon, son of Macbed and the family name derived from Mac Absalone - 'son of Absalone'. There are however, other interpretations of how the name has evolved, including that the initial immigrant to Scotland was Buey Anselan, son of O'Kyan, King of Ulster, who became Buey Anselan, Dominie de Buchanan when granted the "lands of Buchanan". A third idea of how the surname came to be is it's Anglicization from a Gaelic name. Many Irish last names were changed to sound more English as time went on, and McCausland is more than likely one of them. The surname "Mac Ausaláin" may have an underlying Gaelic personal name, possibly Caisealán, meaning ‘little one of the castle’. Although the exact origins are still unclear, most all of today's McCauslands are descended from the McCauslands of Ulster, Ireland. Most people with the surname McCausland or one of its variants refer to themselves as Irish. Although, some McCauslands with Protestant rather than Irish Catholic heritage sometimes refer to themselves as Scotch-Irish. http://en.wikipedia.org/wiki/McCausland_(surname)

Came to Scotland from Ireland, circa 1016, and was granted his lands by King Malcolm in return for fighting the Danes with said monarch. Anslelan O'Kyan, son of O'Kyan, Provincial King of Southern Ulster, left his father's kingdom circa 1016, and, having fought with King Malcolm II of Scots against the Danes, recieved from that monarch the lands of Pitwhonidy and Strathyre in the Parish of Buchanan, becoming the first Laird of Buchanan in the process. He had one son, his heir, John.

Other source: Anselan (or Absolon) Buey (or fair Okyan or Bocainain, anglicized Buchanan.) According to the Clan Buchanan History (circulated by the Clan Buchanan Society in America): It is said, that after seven centuries of raiding, the Danes, under Swein The Fork Beard took control of most of England and Ireland in 1013 and 1014. His son, Canute (994-1035), was to be made King of England. Swein ordered celebrations which were to be held in Limerick, Western Ireland, now Eire, and instructions were given for 1,000 beautiful daughters of the Irish nobility to be present. Instead, however, the same number of Irish youths were dispatched, disguised in women's habits, with long Irish Scains (daggers) concealed below their cloaks. A massacre of the Danes followed. One of these youths was Buey Anselan O Kyan, or O Cahan, which is pronounced O Kane, son of the King of the Fourth Part of Ulster (Northern Ireland). In 1016, as a result of this exploit, he fled Ireland and emigrated to Argyll in Scotland. Eventually he acquired lands in the Lennox, either by marriage, or as a reward for services rendered to King Malcolm II of Scotland (1005-1034). Lennox was broadly known to extend from Glenfruin in the west to Fintry in the east. In addition, Anselan was granted Arms practically identical to those used by the Buchanan Society of Scotland today. All records of Irish insignia have long since disappeared. The story of the same battle is told therein as follows: Sueno or Canutus, at this time king of England, and Denmark, his birth-day approaching, which all the Danish officers and soldiers in Ireland resolved to solemnize with great jollity, Turgesius, the Danish general, sent orders to all the Danish officers in Ireland to repair to Limerick, being their principal garrison and his residence, to assist at the solemnity, fearing nothing that the Irish would or could do in such low circumstances. The general at the same time sent orders to the Irish nobility and gentry, to send to Limerick against the king's birth-day a thousand, or as others say, two thousand of the most beautiful of their daughters, to dally with the Danish officers at that festival. Of this the Irish king getting intelligence, resolved to send the desired number of the most clear complexioned youths could be found, clothed in women's habit, with long Irish skeins, or daggers, below their clothes, with orders that, so soon as they went to bed with their several paramours, being generally drunk on such occasions, they should stab them with these concealed daggers, and afterwards seize upon their guard-house, where their arms were laid by, and if the matters succeeded, to give a signal by kindling a large fire upon the town wall; the Irish king with a small party being absconded in a wood near by, in expectation of the event. The Irish viragoes put their orders in execution to the utmost, and having given the concerted signal to the king, introduced him and his party to the town, who, without any mercy or resistance, killed all the Danes in the garrison, being destitute of sense, officers, and arms, reserving their general Turgesius for further punishment, which was inflicted upon him by drowning, which then, and as yet, is reputed the most ignominious death among the Irish. Most of all the other Danes throughout the kingdom were shortly after cut off. This massacre was a kind of parallel to another of that nature committed on the Danes in England some little time before this, by command of Ethelred, the English king. But, as that, so also this fell short of the success projected thereby. For no sooner was the Danish king of England informed of his countrymen's disaster, than he sent a powerful army into Ireland, which with the utmost rigour did prosecute all who had any hand in this late tragedy; so that most of them fell victims to the rage of their inveterate enemies, and those who did not were necessitated to abandon their native country. Of those who were required to leave Ireland, Anselan Buey was one. He landed in Argyllshire, near Lennox, Scotland around 1016 and became the first laird of Buchanan. In addition, "the greater part of the estate of Buchanan was given to the same Anselan, by king Malcolm, with other lands, in reward of his service against the Danes." The arms given to Anselan, "upon account of his descent, and more especially upon account of his heroic achievements, are, in a field Or, a lion rampant sable, armed and langued gules, holding in his paw sabre, or crooked sword, proper."

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Wikipedia:

Anselan O Kyan, who was a son of one of the Kings of Ulster, landed on the northern coast of Argyllshire, near the Lennox, about the year 1016. Assisting Malcolm II of Scotland in repelling his old enemies the Danes, on two different occasions. Upon their arrival in Scotland, he received a grant of land in the north of Scotland, East of Loch Lomand. The beginning of the Buchanan clan can be traced back to him.

Succession of Clan Buchanan Chiefs

The first six Clan Chiefs are poorly represented in historical records and are included by some Clan historians and omitted by others. Buchanan of Auchmar and Guthrie Smith commence their respective numbering of Chiefs at a different person, and describe a different order and number of Chiefs following Sir Walter 11th of Buchanan. In part this is due to the heir apparent not succeeding to the chiefship before he dies and chiefship passing directly from grandfather to grandchild. The following lineage reconciles Guthrie Smith and Buchanan of Auchmar and their respective numbering is in parenthesis.

1st – Anselan O'Kyan,[62][63] son of a petty king from Ulster, Ireland, in the service of Malcolm II of Scotland from whom he received a grant of land in Lennox. He married an heiress of Denniestoun and by her had a son, John. 2nd – John,[64] whose son and successor was Anselan. 3rd – Anselan,[65] whose son and successor was Walter. 4th – Walter,[65] whose son and successor was Girald. 5th – Girald also called Bernard,[65] whose son and successor was McBeath. 6th – McBeath (MacBethe/McBeth) McCausland,[65] whose son and successor was Anselan. http://en.wikipedia.org/wiki/Clan_Buchanan

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McCausland (surname)

McCausland (Mac Ausaláin in Gaelic), meaning "Son of Absolom" is a surname of Irish and Scotch-Irish origin. The family came from Ireland to the Loch Lomond region of Scotland sometime before the twelfth century. They are said to have settled through a charter on the island called Clarines - Clarich, in Loch Lomond. In one version of how the surname came to be, the name is reputed to come originally from Absalon, son of Macbed and the family name derived from Mac Absalone - 'son of Absalone'. There are however, other interpretations of how the name has evolved, including that the initial immigrant to Scotland was Buey Anselan, son of O'Kyan, King of Ulster, who became Buey Anselan, Dominie de Buchanan when granted the "lands of Buchanan". A third idea of how the surname came to be is it's Anglicization from a Gaelic name. Many Irish last names were changed to sound more English as time went on, and McCausland is more than likely one of them. The surname "Mac Ausaláin" may have an underlying Gaelic personal name, possibly Caisealán, meaning ‘little one of the castle’. Although the exact origins are still unclear, most all of today's McCauslands are descended from the McCauslands of Ulster, Ireland. Most people with the surname McCausland or one of its variants refer to themselves as Irish. Although, some McCauslands with Protestant rather than Irish Catholic heritage sometimes refer to themselves as Scotch-Irish. http://en.wikipedia.org/wiki/McCausland_(surname)

Added by; HRH Prince Kieren de Muire von Drakenberg