One thing I really admire about JK Rowling's writing in the Harry Potter books is how even her made-up words sound natural. Voldemort. Horcrux. Dumbledore. Hogwarts. They've got a natural rhythm and flow to them that can be really difficult to pull off, but the books are full of them and they all sound like they belong. I wish I were as good at making up words as that.
Mokalus of Borg
PS - And they've all got a similar feeling to them, like they belong together, too.
PPS - I don't know if that's by design or because they're all Rowling's words.