I've seen in multiple fanfictions and other places the joke that Sirius and/or James wanted to name Harry Elvendork, stating that it was unisex. Is this from canon or Word of God, or just something created by the fans but spread widely?
‘Names?’ repeated the long-haired driver. ‘Er – well, let’s see. There’s Wilberforce… Bathsheba… Elvendork…’
And near the end:
‘Yeah, nice meeting you!’ said James. ‘And don’t forget: Elvendork! It’s unisex!’
It was written by Rowling for auctioning off for charity. I don't know whether most fans consider it canon. If you want to consider it canon, then do so. It doesn't say that they were going to name Harry Elvendork, but it does refer to it as unisex.
I've been in Harry Potter fandom since 2002 and I've never heard the term "Elvendork" in relation to Harry. Seems more appropriate for Legolas, were Legolas to have a ridiculous nickname.
There is this from Half-Blood Prince, though, which makes me laugh:
‘Have you ever heard of someone called the Half-Blood Prince?’
‘The Half-Blood what?’
‘Prince,’ said Harry, watching him closely for signs of recognition.
‘There are no wizarding princes,’ said Lupin, now smiling. ‘Is this a title you’re thinking of adopting? I should have thought being the “Chosen One” would be enough.’
‘It’s nothing to do with me!’ said Harry indignantly.
Half-Blood Prince - page 315 - Bloomsbury - chapter 16, A Very Frosty Christmas
Also, Draco calling Harry "'The Boy Who Scored" ... or whatever it is they're calling you these days ...'" is a bit amusing.
I don't recall "Elvendork" in any of the Harry Potter books, nor has the term come up in any J.K. Rowling interview I've ever heard or read. I don't know how widely spread it really is, but if it is ubiquitous it's probably propogated by the fans at this point. That said, I encourage you all to throw your votes to Ike! :D