Pictish Language

 

The real question is what language did the Britons speak. And the most modern idea is the tongue they spoke, similar to that of the Gauls, was a pre-indo-european tongue that developed in Europe in the Bronze age, possibly imported from western Anotolia by proto-indo-european speakers.

 

The word Pict itself derives from the Greek word Pretani (painted one) as does the word Britani (Briton). Roman mis-pronuciation of Greek turned one word into two.

 

 

I forgot to explain it: The Brits pronounced Cruithin as Pruithin which the Romans corrupted into Pretanni (or something similar).

This would make sense considering to the south there was Ystradd Clyd (modern Strathclyde) and Gododdin (modern Lothians region) which were both Brythonic kingdoms.

 

An example is Aberdeen (fort on the Aber).  Deen in Pictish is considered related to the Brythonic word Din meaning fort.  Dundee (Fort on the river Dee), Dunedin (fort of Edin) the ancient Brythonic name for Edinburgh before it became Anglic and Dunbarton (Fort of the Britons) are examples of Brythonic names names in Scotland which has Din.

 

My guess is that as the linguistic and cultural flow of the Brythons spread among the native inhabitants of mainland Britain it gradually got weaker the further north it spread and was weakest in the Northern parts of modern Scotland which would explain why they were culturally different and had a weaker link with the Brythonic language. 

 

All native people in Britain would have been genetically similar but language and culture would be affected by exposure.  With the Pict's in the remote highland that exposure would have been lesser.