[He doesn't know what a Planet is? How interesting! She smiled at that though, wondering if the World or Planet Arda is someplace she and the Doctor can check out. She knows nothing of it, but she likes to take a peek at new places.]

Middle-Earth? We have a term like that where I am from, but it's to note a era of the long since past. [Or even Mythical Past, but she doesn't say that.]

I think eccentricity is a really great word for this adventure.