"Celt" Conjecture

[Phaichtos]

Just to clarify, that is absolutely not what I am suggesting. I think, as an ethnic name, it was restricted to parts of Gaul and Iberia.

Okay, fair enough! An argument I might buy, on the other hand, and what you might be suggesting, is that what was originally perhaps an ethnic name here and there (or even, indeed, a common enough personal name or even phrase) was extended by outsiders (Greeks and Romans) to peoples who may have bore some passing similarity to each other. This is documented fairly often in the later context of European expansion to other parts of the world.