The author of the description, who is usually supposed to have been Giraldus Cambrensis, but whose etymologies show him to have been evidently a Welshman and acquainted with the Welsh language, gives us four interpretations of the name Arregaithel. He says it is so called as ‘the margin of the Scots or Irish,’ for all the Irish and Scots are generally called Gattheli, from their original leader _Gaithelglas_; or because the Scotti Picti first peopled it after their return from Ireland;[48] or because the Irish occupied these parts after the Picts; or, what is more certain, because that part of the country of Scotia is more closely connected with the country of Ireland. In the Irish Annals the form of the name is _Airergaidhel_, _Airer_ signifying a district.[49] The Scotch form is _Earrgaoidheal_ from _Earr_, a limit or boundary, and this approaches most nearly to the form of the name in the old description, with its etymology of margin or limit of the Gael. The oldest name is that probably in the Albanic Duan, where it is termed _Oirir Alban_, or the coast lands of Alban, from _Oirthir_, a coast or border; and we find the name _Oirir_ applied to it in the Book of Clanranald, which distinguishes the _Oirir a tuath_, or northern Oirir, and the _Oirir a deas_, or the southern Oirir, from each other. The name given to this district by the Norwegians was _Dali_ or _Dalir_, the Dales, and Somerled, the Regulus of Arregaithel, and his family, are termed in the Orkneyinga Saga the _Dalveria Aett_, or family of the Dales.[50] [Sidenote: Districts ruled by kings and afterwards by Mormaers.]