Old World

In the real world, Old World is a fancy way to refer to the continents of Europe, Asia, and Africa, as opposed to the "New World" (the Americas and Oceania). That definition was coined by people who lived on those continents; to them, their landmass was "old", and the continents on the opposite side of the world from them were "new". They also placed themselves at the middle of their world-maps, which, in a roundabout way, lead to the naming of J. R. R. Tolkien's Middle-Earth.

The nations of Warhammer Fantasy Battle use the term almost identically -- the "Warhammer World"'s equivalent of Eurasia and Africa (home to the Empire, Cathay, Kislev, and others) is the Old World, compared to the New World of Lustria.