ANGUS, a very ancient name in Scotland; the first on record who bore it being the brother of Loarn and Fergus, the earliest kings of the Dalriadic Scots. Pinkerton says: "The Irish accounts bear that Loarn, Angus, and Fergus, three sons of Ere, led the Scots back to Britain in 503, (after having been compelled to retreat to Ireland about fifty years before—that is, about the middle of the fifth century, or about two hundred years after their first arrival in Argyleshire,) and that Loarn was the first king and was succeeded by Fergus. What became of Angus we are not told. It would seem that, either from incapacity or preference of private life, he aspired not to any share of the power of his brothers. But though Loarn be left out of the regal list in the Scottish accounts, yet neither he nor Angus is unknown to them. Fordun, lib. iii. cap. i., says that Fergus, son of Ere, came to Scotland cum duobus fratribus Loarn et Tenegus, ‘with his brothers Loarn and Tenegus,’ which last word is a not uncommon corruption of Angus with Fordun. The register of the priory of St. Andrews, written about 1250, also says of Kenneth, son of Alpin, sepultus in Yona insula, ubi tres filii Erc, sciliet Fergus, Loarn et Enegus, sepulti fuerant; lie was buried in Ions, where the three sons of Erc, namely Fergus, Loarn, and Enegus were buried.’" (Enquiry into the History of Scotland, vol. ii. p. 92.) It would appear that Cantyre, (from the Gaelic word Ceantir, Headland), was the portion of Fergus, Loarn possessed the district called after him Lorn, and Angus is supposed to have colonized Islay, as it was enjoyed by Muredach his son, after his decease. See LORN, marquis of, and ARGYLE, duke of; also DALRTADA. ANGUS, styled by the annalists Angus MacFergus, was also the name of the most powerful king the Picts ever had. He reigned between 731 and 761, in which latter year he died. Belonging originally to the southern Picts, he had, in 729, raised himself to the command of that portion of the Pictish tribes, and in the year 731, by the conquest of Talorgan MacCongusa, his last opponent, he obtained the throne of the whole Pictish nation. In consequence of his success a league was entered into between the principal tribes of the northern Picts and the Dalriads or Scots of Argyle, who were ever ready for war with their Pictish enemies. Angus, however, crushed this formidable union, and almost annihilated the Scots of Dalriada; "and yet," says Skene, "it was his power and his victories which laid the germ of that revolution that resulted in the overthrow of the Pictish influence in Scotland." (History of Highlanders, vol. i. p. 55)http://www.electricscotland.com/hist...tion/angus.htm

You can read all the information here: