Clan Gunn Origin - the original tribe of Sutherland
Smibert (1850) gives a sensible Clan Gunn origin possibility namely that Clan Gunn are the original inhabitants of Sutherland (rather than the absurd Clan Gunn Orkney Islands / Norway / Vikings origin idea). Smibert's idea goes well with the Caereni tribe in the Sutherland area (Ptolemy 150 CE).
See https://archive.org/details/clanshighlandss00smibgoog for Smibert's book.
See http://clangunn.weebly.com/real-origin-of-the-clan-gunn.html for greater discussion of this idea.