Concerning the Origin of the Clan Gunn
...'the most probable descent of Clan Chattan is from these ancient Picts'
Page 5, MacPherson of Dalchully, The Chiefs of Clan MacPherson.
Given the great Clan Chattan descended from a tribal Pictish group it's quite logical for more clans to descend from the Picts, such as the Clan Gunn.
In my view the origin of the Clan Gunn is best seen as being that of a non-tribal group of the original inhabitants of Strathnaver / Sutherland / Caithness.
See http://clangunn.weebly.com/real-origin-of-the-clan-gunn.html for more information.
Concerning the Clan Gunn surname
'Surnames as we understand them today did not come into general use in the Highlands until the 17th century.'
Page 16 Margaret Maclaren of MacLaren's 'The Maclarens A History of Clan Labhran'.
But yet we are meant to believe that the surname Gunn originated from a man who died no later than 1240, in Norway, some three to four hundred years before surnames became fixed in the Highlands. It's just not possible. The surname Gunn has no Scandinavian / Orkney origin.
I have dealt with this issue many times, but thought I would add a new source.
I've just acquired a copy of 'Under a Regent Moon' by Tim Williams and Kevin Kenneally which includes Aeneas Gunn's 1899 account of his time in the Kimberley region of Western Australia. It looks superb. Aeneas Gunn descended from the Gunns of Osclay (Caithness), as do I. Aeneas Gunn's wife is better known than him with her 'We of the Never Never' being an account of their later time in the Northern Territory, and other texts.
Aeneas Gunn's family trees - as discussed in the Appendix of Thomas Sinclair's 'The Gunns' - can (overall) be found on this site.
For those who have not seen the news - the Scottish Nationalist Party won in a landslide in Scotland (although the Conservatives won the overall election). See http://www.bbc.co.uk/news/election-2015-scotland-32635871
For those interested in final polling for the election, detailed - and knowledgeable - commentary on election day and excellent analysis as the results are announced I recommend http://ukpollingreport.co.uk/
The Scottish Nationalist Party is still odds on for a stunning result...
The election for the British Government is very soon and the SNP polling has held up. The most recent poll gives them 49% - for full discussion (including that of a possible further 'Scotland independent' referendum) see http://blog.whatscotlandthinks.org/2015/05/yougov-snp-surge-holds-steady/