@FfaerieOxide@Arotrios I mean I don't know anything about Welsh, so I can't be anymore help than that. I noticed it in Yeats' "Folk and Fairytales of the Irish Peasantry" as well. I would look up words for pronunciation and find no such word existed, but a similar one with different spelling did.
@Arotrios@FfaerieOxide its not unusual for translators in that time to print Anglicized approximations of words instead of their actual spelling. I figure it's because they assumed their audience would not otherwise know how to pronounce it.