Many of those familiar with J. K. Rowling's Harry Potter books, or the films based on them, have been surprised to discover that the name of the headmaster of Hogwarts School also occurs in Tolkien's writings. (They might be even more surprised to find it in Thomas Hardy's The Mayor of Casterbridge.) The word is recorded by the OED as a dialect name for the bumblebee (and certain other insects), with quotations dating back to 1787. Tolkien used it in some versions of his poem 'Errantry', in which the 'merry passenger', we are told, 'battled with the Dumbledores' (HME VII. 86, 88).
The Ring of Words
Tolkien and the Oxford English Dictionary