Krabappel's Klassroom

I have been reading, off and on, Yeats' [Irish] Fairy and Folk Tales [of the Irish Peasantry].* Here are some (curious, interesting, or surprising) things that I learned, directly or indirectly, as a result:

• Tir na nOg is analogous to Tolkien's Undying Lands. I wonder whether it was inspirational.
• gumption seems to be of Celtic origin. The free online dictionaries I use attribute it originally to, if anything, Scottish; but it came to my notice as an apparently Irish word in a book of Irish folklore compiled by an Irishman.
• I wonder whether the same might be true of knickknack. The free dictionaries don't mention a source language. The use of nic-nackenes in the book might be a borrowing from English by Irish, or vice versa.
• It was in urban fantasy novels that I first encountered references to the Seelie and Unseelie Courts of fairies. Yeats does not discuss them, and the terms themselves appear to be of Scottish origin: so, although I have encountered modern fantasy that affiliates Irish fairies with one Court or the other, I wonder if that might be a conflation.
• Fairies and elves are not the same thing. Fairies are Celtic and elves are Germanic. One school of Irish folklore holds that the (early-)modern fairy is the diminished descendant of the Tuatha de Danann, the residents of Ireland immediately preceding humans. Like Tolkien's elves, the Tuatha were, or could be, stately and regal. While many of the gentry in Irish folklore appear smallish and rude, there are others (apparently largely of Yeats' "trooping," i.e., non-solitary category) who can appear as both churl and aristocrat (it is unclear to me which form is thought to be real and which illusory, or glamourous). It has been some time since I read any Norse folklore, but I do not recall that the elves (or, indeed, the gods) were particularly stately or regal. It rather seems as though Tolkien appropriated fairies of the character of the Tuatha and renamed them "elves." Given the popular fairy-image testified by positive responses to the Cottingley fairies—an image that Disney used to complete the ruination of the Celtic fairy—I can comprehend a desire to distinguish the Middle-Earthly ones.
• I suppose fairies, elves, gnomes, sprites, and all were smooshed together into an undistinguished menagerie by the American melting-pot of the late 19th and early 20th centuries.

___________
*I own it with the title Irish Fairy and Folk Tales. The other seems to be its original 1888 title.