[3] The earliest reference to the title is however to that of a native Scots ruler, Donnchad, although the extent of the Scottish crown's influence so far north at the time, beyond the lands of the powerful Mormaers of Moray, is questionable.

The Pentland Firth, between Caithness and Orkney, was a stretch of water which divided the two earldoms but also united them, especially perhaps for the Norse, whose command of the seas was an important aspect of their culture.

[7][a] Even in the mid-12th century it appears that a king of Norway - Eystein Haraldsson - had no difficulty in capturing Harald Maddadson, an Earl of Orkney, from his base in Thurso, Caithness.

[11] The title Earl of Caithness was granted to David Stewart, a younger son of the Scots king, and the mormaerdom effectively continued as an earldom from that point onwards.

[4] In 1098 Magnus Barefoot, King of Norway deposed the Thorfinnsson brothers as Earls of Orkney and set his 8 year old son Sigurd Magnusson up in their place.

[33] After the failure of Harald the Younger, c.1200 William of Scotland then asked King of the Isles Rognvaldr Gudrodsson (Raghnall mac Gofraidh) to take Caithness on behalf of the Scottish Crown.

[54] Although not descended from previous Orcadian earls, Rognvaldr was related to these Norse magnates through his paternal grandfather's marriage to Ingibjorg, daughter of Haakon Paulsson.

[57] Jon Haraldsson's son Harald had drowned in 1226 and as there were no male heirs two parties with a claim sought the jarldom from King Haakon Haakonsson of Norway.