JK Rowling once mentioned in a Harry Potter special edition of Newsnight that the Death Eaters were originally called the Knights of Walpurgis.
Jeremy Paxman: And these scraps of paper which you've filed elegantly in a carrier bag, they're plot ideas or...
JK Rowling: Well some of them are totally redundant now because its been written and I keep them out of sentimentality's sake, I suppose. But some of it has backstory in it like this - in here is the history of the Death Eaters and I don't know that I'll ever actually need it - but at some point - which were once called something different - they were called the Knights of Walpurgis. I don't know if I'll need it. But I like knowing it. I like to keep that sort of stuff on hand.
(Newsround; Full Transcipt of JK's OOTP Interview).
Now I'm aware of the mythology and the traditions around Walpurgis Night. I'm interested in whether JK Rowling herself has passed further comment on this in any way - whether through a Pottermore article or another interview. Has she?