|The kilt of course is completely ahistorical|
Fergus Mór mac Eirc (Scottish Gaelic: Fergus Mòr Mac Earca; English: Fergus the Great) was a legendary king of Dál Riata. He was the son of Erc. While his historicity may be debatable, his posthumous importance as the founder of Scotland in the national myth of Medieval and Renaissance Scotland is not in doubt. Rulers of Scotland from Cináed mac Ailpín until the present time claim descent from Fergus Mór. The historical record, such as it is, consists of an entry in the Annals of Tigernach, for the year 501, which states: Feargus Mor mac Earca cum gente Dal Riada partem Britaniae tenuit, et ibi mortuus est. (Fergus Mór mac Eirc, with the people of Dál Riata, held part of Britain, and he died there.) However, the forms of Fergus, Erc and Dál Riata are later ones, written down long after the 6th century. Fergus is also found in the king lists of Dál Riata, and later of Scotland, of which the Senchus Fer n-Alban and the Duan Albanach can be taken as examples. The Senchus states that Fergus Mór was also known as Mac Nisse Mór. These sources probably date from the 10th and 11th centuries respectively, between 30 and 40 generations after Fergus may have lived. While it was suggested some believe Fergus claimed lineage to Arthur, the historian John Morris has suggested, instead, that Fergus was allowed to settle in Scotland as a federate of Arthur, as a bulwark against the Picts.
Here's what wikipedia says about Carrickfergus:
Carrickfergus (from Irish: Carraig Fhearghais, meaning "rock of Fergus"), known locally and colloquially as "Carrick", is a large town in County Antrim, Northern Ireland. It is located on the north shore of Belfast Lough, 11 miles (18 km) from Belfast. The town had a population of 27,201 at the2001 Census and takes its name from Fergus Mór mac Eirc, the 6th century king of Dál Riata. It is County Antrim's oldest town and one of the oldest settlements in Northern Ireland as a whole.