I haven't seen any of the team's Celtic experts lately, so I am afraid your question won't be answered. However, as I understand it, the quotes have been taken from a work that one of them is currently translating. I also know that many of the "barbarian" units have been created based on archeological finds rather than written or oral history. However, I do admit I am puzzled about the Uachtarach Dubgaoscacha as well.