Bob
Don`t know if you remember, but you and I left unfinished an interesting conversation on the nature and origins of myth, long ago. I am glad you enjoyed my post: really we, amateurs, feel at loss before the huge amount of theories and arguments that the arrival of DNA studies have prompted.
Art
Thank you for the compliments
It is the Romans who recorded the very word. If we are using it today, it is only because it is found in Roman sources so, how could they be "wrong"?. However, it is funny that the personal name "Celtius" was common in the western half of the Iberian Peninsula including Asturias, as we know through ancient inscriptions on pottery and gravestones. This makes likely, in my view, that the word was taken from the locals. Incidentally, the Romans never claimed that Britons or Hibernians (Irish) were Celts. Neither were, it seems, all of the Gauls, only those living in "Galia Celtica".
Now, can we give for certain that these "Celts" were the ones who unified the old cultural layer that we West Europeans all share in common? Nope. However:
-The ONLY mythical cycles which have survived from Pre-Christian times in West Europe were noted down in Celtic Languages (The Ulster Cycle, the Finnian Cycle, the Mabinogion)
-These mythical cycles clearly derive from an original tradition, totally apart from Germanic Eddas or Greek-Roman myths.
-It is not difficult to paralell these Celtic myths from the Isles and many traces of pre-Christian beliefs in the continent, both earlier and later. The Irish Lugh is the same as the Gaulish-Celtiberian-Asturian Lugus, for example, and many motifs from the Mabinogion or Irish Epic can be found in French medieval lays and in modern folklore from all over West Europe.
To sum-up:
1 We know that there is a common tradition in West Europe, totally independent from Roman heritage and older than it.
2 We can track the last traces of this tradition mainly through sources written in Celtic languages, as well as hints in Roman sources always referred to "Celtic tribes" such as Gauls and Celtiberians
3 We know for sure that this old cultural layer has a strong personality, and that it is quite different from Germanic or other European cultures.
Now, how could we name this wide, amazing, misterious phenomenon, this brotherhood of West European aboriginals which has survived down to our days?
Celtic culture, of course.