Of all the original words created by J. K. Rowling in the Harry Potter books, the only words that have so far made their way into the online Oxford English Dictionary are the words muggle, quidditch, Butterbeer, and hippogriff. Look up the meanings of these words in the $O E D$ and speculate on why they have made it into the $O E D$ as opposed to other Harry Potter words like house elf, bludger, or dementor.