Now they come across sort of Irish.

One of my favourite authors is Brian O'Nolan, who wrote under the pseudonyms Flann O'Brien and Myles na gCopaleen. Under the former, he wrote a terrific novel "At Swim Two Birds," which at various points is a parody of medieval Irish literature (there's a classic sequence of Mad Sweeney being used at the same time as two stereotypical Wild West cowboys). Under the latter, he wrote a regular newspaper column for the Irish Times (Dublin), which often delved into Irish (and was sometimes written in Irish). One novel of his, "The Poor Mouth," was in fact written in Irish and only recently became available in translation. (There's a publishing house called the Dalkey Archive, after one of his books, which has much of his oeuvre in print.)

The use of the Irish here is derived from the way O'Nolan/O'Brien used it, and is meant to show that the language of Elfhame is a bit different from the Standard Elvish used everywhere else.

Side note: my literary historian uncle Peter Costello (father's younger brother) co-wrote the last biography of O'Nolan. He also has a number of other books, including "The Magic Zoo," which is a survey of "fantastic and mythical creatures."