Interesting. I honestly can't say I can guess what it pretains to. Perhaps Godric's Hollow, which is where Harry's parents were killed.
When I first heard the name for book 7 my mind was racing with possibilities as to who the Half Blood Prince could be. I remember thinking it would be either Malfoy (assuming that maybe he really wasn't pure blood afterall...which was a stupid guess) or Hagrid. I don't think anyone would have guessed it would be Snape.
I absolutely cannot wait for this book. There's so much stuff that HAS to happen in it. I mean, I believe Harry will go back to school possibly after spoiler (click to show/hide)
talking to Dumbledore's portrait
-Harry will go to Bill and Fleur's wedding pretty early in the book
-He'll turn of age
-He'll visit Godric's Hollow
-Seek out the identity of RAB spoiler (click to show/hide)
(which MUST be Sirius' brother)
That's the core stuff that's fact. But there's a lot of stuff left. For instance, is Harry going to return to Grimwauld, and possibly start his horcruxes hunt there? Reading back on OOTP reveals that the house has at least one horcrux in it (the locket Harry and Ron couldn't open while cleaning up the house).
But how will Harry go to school and search for the horcruxes, outside of the ones he finds before the school year starts? In HBP he was able to search for them with Dumbledore at night without compromising his studies (The Cave), so perhaps he'll do it that way.
Can't. Fucking. Wait.
And finally, spoiler (click to show/hide)
SNAPE IS A GOODGUY