Maybe not Gaelic, but there is no reason why Devonians should not have hung on to a Brithonic language long enough to use 'lyn' in the same way that the Welsh use "llyn". The Cornish did, and they are only a few miles further west!
There is also 'Lindow' in Cheshire- the black lake of sacrificial drowning fame.
It is fascinating to me that many hills in the Peak District are called "Low". Arbor Low with it's stone circle, Shuttlingslow etc. Again,in Welsh, that would be 'llaw' - hill.
I thought it was very interesting when there was a genetic map of the UK on TV a couple of years ago which showed that around two thirds of the population of Britain are descended from the original hunter gatherers who crossed from mainland Europe before the flooding of the Channel and North Sea. It also pointed out that there was no way to tell the difference, genetically, between those who had arrived at that time and those who arrived later from the Low countries- i.e. Angles, Saxons, Jutes and Danes.
We are a bunch of mongrels and that's a fact.
I rejoice in that.