the genitive is "na Graonlainne". both names are the same in Irish, in fact.

I'm not certain where "An Aetiòp" came from - it may be a borrowed spelling from Irish. My 1992 Bible calls it "Etiopia", with the genitive "na h-Etiopia". I would imagine this is used more in the language than "An Itiop", but I have never discussed Ethiopia in Gaelic before.

Even if you for some reason don't agree that these are the standard names in Gaelic, you should be adding them as alt_name since they clearly have currency in the language. Removing them entirely is borderline vandalism, especially if you are only doing it for matters of consistency, which is a useless metric. Many countries don't really have established names in Gaelic and may use several different ones - it is not for you or I to decide which one is the only one listed on this website.