Wordplay

There's so much that is amazing in HP that it's hard to hit all of the supa-cool things, but I've always admired the naming conventions of JK. In 5 out of 7 books, the big mystery of the book revolves around the book title, and even in the two where the meaning of the title is revealed early in the book, in on there are still mysteries that involve the object in the title. And the one that who's title doesn't involve mystery is my favorite book, so I don't really care. In fact, it might be the lack of driving mystery that helps it to be my favorite.

Usually in the books, Rowling takes something that we're familiar with and can understand and make guesses. This last one was different for me, though. I couldn't quite grasp the "deathly" part of the title because we don't really use that word much on this side of the pond (I'm not really sure if they do on the other side, honestly). Nor, really, do we use the word "hallow."

While I now understand the use of "hallow," I'm still not sure about "deathly." Could somebody please explain it to me? (In email, not here, since this is a spoiler-free zone). In fact, more to come later on how much I hate spoilers.