Added Oct 13, 2014: This was originally something I was going to return to and finish, but that was back before this book was packed up into storage. And the annoying part is that what I was dying to post quotes from was the part on pornography, which had all sorts of fun examples from historic texts (many of which would seem wildly tame now).
Anyway, if you ever bump into this book, buy it if you're an English major because even if you don't have a concrete purpose for any of the information in your various classes and papers, you will definitely enjoy poking around in here. And if you're not an English major take a look anyway - you might find enough to convince you to read more. Especially if you love discovering new words and their origins.
These two similar words also seemed vaguely seasonal, though not exactly in the definition (nothing scary or spooky here):
ghostword (p. 286): A term invented by W. W. Skeat, the great 19th c. editor of medieval texts, to describe words which have no real existence. Such spurious words are often the result of inadvertent errors made by copyists, printers and editors. [wikipedia - which gives examples]
phantom word (p. 503): A word that exists through the error of a scribe, printer or lexicographer, or merely through some corruptive influence. Examples are: willy-nilly for will he? nill he?; whatnot; dacious for audacious; obstropolous for obstreperous; brecksus for breakfast. Bacon and eggs and ham and eggs are inclined to appear on European menus as bekendecks and hemenex, and in other variations.
Randomly the words bekendecks and hemenex don't seem to occur often - that I could dig up via google anyway.
Seasonal link I bumped into: World Wide Words on Ghoulies and Ghosties