Hello

I'm not completely sure about this but I remember reading somewhere about the link that can be shown between Gaelic/Gallic and other Indo-European languages through the roots of certain words. I think they went back to the sanskrit roots though I'm not sure about that.

From memory the only word that springs to mind is the word for king in different Irish Latin and the word used in India:
ri/rex/raj.

I think that the underlying reason was that Gaelic/Gallic was at an extreme geographical end of the territory of Indo-European languages so had perhaps not evolved or mixed with other languages or developed beyond its roots as much as other languages might have.