rivervox asked: I noticed that you use "dwarfs" in the US version of "Fortunately, the Milk" and wondered if that is your preferred spelling, or if the copy editors chose it. We enjoyed the book greatly, especially the wumpires.
It’s the plural of dwarf.
Tolkien made up the word dwarves, to show that he was referring to a race of people. (http://grammarist.com/usage/dwarfs-dwarves/ ) Other people have used it since, most of them probably assuming that it was the true plural. (And Sondheim plays with dwarfs/dwarves in his song Agony, which you can watch at http://youtu.be/UAPJTik5mSo)
And for the etymologically interested: via http://www.etymonline.com/index.php?term=dwarf
dwarf (n.) Old English dweorh, dweorg (West Saxon), duerg (Mercian), “very short human being,” from Proto-Germanic *dweraz (cf. Old Frisian dwerch, Old Saxon dwerg, Old High German twerg, German Zwerg, Old Norse dvergr), perhaps from PIE *dhwergwhos ”something tiny,” but with no established cognates outside Germanic. The mythological sense is 1770, from German (it seems never to have developed independently in English).
Whilst in this and other ways the dwarfs do at times have dealings with mankind, yet on the whole they seem to shrink from man; they give the impression of a downtrodden afflicted race, which is on the point of abandoning its ancient home to new and more powerful invaders. There is stamped on their character something shy and somethingheathenish, which estranges them from intercourse with christians. They chafe at human faithlessness, which no doubt would primarily mean the apostacy from heathenism. In the poems of the Mid. Ages, Laurin is expressly set before us as a heathen. It goes sorely against the dwarfs to see churches built, bell-ringing … disturbs their ancient privacy; they also hate the clearing of forests, agriculture, new fangled pounding-machinery for ore. [“Teutonic Mythology,” Jacob Grimm, transl. Stallybrass, 1883]
The shift of the Old English guttural at the end of the word to modern -f is typical (cf. enough, draft). Old English plural dweorgas became Middle English dwarrows, later leveled down todwarfs. The use of dwarves for the legendary race was popularized by J.R.R. Tolkien. As an adjective, from 1590s.