Following up my earlier post, the Tuatha De Danaan do come to
mind here. The teuto-word, plus some reflex of the da-/dan- root. I've not
studied Celtic mythology much, but the Tuatha De Danaan seem to have been
mythical from the start, stories from earlier times on the continent, preserved
and retold in Ireland, with the places shifted largely to Ireland.
Is it fair to say 'Danaan' should be seen as a fundamental IE
ethnonym, at the level of say 'Aryan', words ancient IE peoples used to
describe themselves?
Mark.