Time to consider Ptolemy's first century Scottish map as it applied to the Gunn area. See the above Blau version of 1654; the tribes are given as Cornabij (more normally Cornavii), Carini, Carnonacae, and Creones / Cernotes. They are accepted as being, at the very least, linked tribes.
Skene in 1836 has them as
Say the first part of the names of the tribes who inhabited Gunn lands in the first century - Kourn, Kairin, Karn and Kreon - and they all sound quite linked to the name Gunn some 1500 or so years later...
It's not impossible to believe that a proto-Gunn name was around in the first century...
The K-G and general spelling issues are irrelevant as the Scottish societies were illiterate and Ptolemaic textual corruption over time will also make life difficult; it is the sound which matters. The second part of the tribal names concern Latin issues of making plurals.