The Scots Gaelic Myth

[Allan Thomson]

Actually looking further but the Brythonnic equivalent of Dun (a vitrified Hill Fort) is said to be Din. So Edinburgh could well be P Celtic in origin.

What's to say during the period of Gaelacisation that some older P Celt place names weren't mangled into Gaelic equivalents (or even something totally different?).

I'd suggest the more Southerly appearances of Dun in Scotland & Northern England are of the Saxon origin or Saxon corruptions of earlier P Celt placenames and not evidence of Gaelic being spoken in those areas.