Coincidentally, I came across the following, from an article by Hugh J. Dawson which originally appeared in the James Joyce Quarterly 25:3 (Spring 1988). The quote is from Thomas McGreevy, a friend of James Joyce:

Thomas McGreevy and Joyce

"Recently one of the interpreters of Finnegans Wake associated the sentence "Silence is in our faustic halls" with The Castle of Dromore (which I take to be the now well-known song, the words of which are translated from the Irish of Dr. Hyde). But I wonder whether The Castle of Dromore was well-known or known at all in the Dublin of Joyce about the first decade of this century. Certainly I never heard Joyce or any member of his family (all of whom sang or lilted Irish songs about the house like the rest of us) refer to it or sing, or even lilt, it. So I think the derivation of "Silence is in our faustic halls is more likely to be from Moore's "Silence is in our festive halls" than the Hyde translator's more remote "But peace reigns in her lofty halls."

If we are to accept the reference in Songs of the Four Nations, quoted above by Masato (there seems to be no reason why we shouldn't), then it would seem that McGreevy was in error in assuming Boulton's text to be a translation from Hyde's Irish; the reverse appears to be the case. This snippet doesn't really take us any further, but I'd best mention it now, in case it returns to haunt us. Hyde and Boulton were contemporaries, Boulton being three years the elder.