Originally Posted by Kyrio

The name twilight being the name of the evil is probably a reference to that dark, yet still visible moment after sunset. The Twilight Realm itself is a very dark place, but it is plainly visible. Darkness represents the unknown and the unknown is mankinds greatest fear. "Twilight" is the moment of darkness in which you can see the strange things that supposedly happen within it...or something like that. as for princess, it could be Zelda because she's trapped in the Twilight, or it could be Midna, because she's the only "resident" of the Twilight that we know. It could also be someone we haven't even seen yet.