Ooh! Celts in Ireland! A favorite topic of mine. Billy explained this brilliantly (as I was typing my own response, but I shall gladly concede to a better explanation!), go rabh maith aige. I wrote a paper on the 'Celts in Ireland' (or not!) for my archaeology course at UCC (first honours!) and I'd like to just add a few more "hmm makes you think" points.
In addition to the lack of evidence in the archaeological for an invasion (which shows up clearly with the Anglo-Normans, etc.) there is evidence for the repeated construction of ritual sites and houses in wood. If Ireland was supposed to be overrun by conquerors at this point, why were the same wooden structures built the same way nine times in nearly four hundred years (at Navan Fort Site B)?
Also of interest is an iron sword found in the Shannon by Athlone. While iron is associated with the continental 'Celtic' people (and why this is called 'the Iron Age') the shape of the sword is similar to the indigenous bronze Gündligen sword. Most interesting is that the edges of the sword were cold-hammered to increase hardness, which was a bronze-working technique. Combined with the linguistic evidence that words for bronze-working became words for iron-working (according to Gabriel Cooney and Eoin Grogan in
Emania 9) I think this is a pretty good sign that local, indigenous bronzesmiths were experimenting with iron on their own.
Finally, the concept that the so-termed Celtic languages could have only gotten to Ireland, Britain, etc. through an invasion is, in my opinion, just a remnant of that 19th c. "facts-be-damned" mashing together of evidence that put us into this Celtic mess. Until quite recently it was vastly easier to travel by boat than by land. The Irish Sea, English Channel, and Bay of Biscay would have been catalysts of interaction and trade. Is it that hard to believe that the 'Celtic' languages are so similar because the cultures would have adopted each other's languages, and eventually the Indo-European one (proto-Celtic) from the continent became the dominant lingo for communication?
Some great sources for information on the Iron Age in Ireland:
Champion, T.C. “The European Iron Age: assessing the state of the art.”
Scottish Archaeological Review 4 (1987): 98-107.
Collis, John. "Celtic Myths."
Antiquity 71 (1997): 195-201.
Cooney, Gabriel and Eoin Grogan. "An Archaeological Solution to the 'Irish' Problem?"
Emania 9 (1991): 33-43.
James, Simon.
The Atlantic Celts: Ancient People or Modern Invention?. Madison, Wisconsin: The University of Wisconsin Press, 1999.
*Ó Donnabháin, Barra. “An Appalling Vista? The Celts and the Archaeology of Later Prehistoric Ireland.” In
New Agendas in Prehistory: Papers in commemoration of Liz Anderson, edited by A. Desmond, G. Johnson, M. McCarthy, J. Sheehan, and E. Shee Twohig, 189–196. Wordwell Books, 2000.
O'Kelly, Michael J.
Early Ireland: An Introduction to Irish Prehistory. Cambridge: Cambridge University Press, 1989.
Raftery, Barry.
Pagan Celtic Ireland: The Enigma of the Irish Iron Age. London: Thames and Hudson, Ltd., 1994.
Waddell, John. "The Question of the Celticization of Ireland."
Emania, no 9. (1991): 5-16.
Waddell, John. “Celts, Celticisation and the Irish Bronze Age.” In
Ireland in the Bronze Age. Proceedings of the Dublin Conference, edited by John Waddell and E. Shee Twohig, 158-169. Dublin, Stationary Office, 1995.
Waddell, John.
The Prehistoric Archaeology of Ireland. Galway: Galway University Press Ltd., 1998.
*I like this book a lot, but a lot of people don't. Apologies if you try it and dislike it.
I hope this helps, Nerva, but it will probably give you a headache
