Arena literally means sand in romance languages (including Latin, the language of the inventors of the arena). Sand in French is Sable. Also, it's a cute little Marten species in Asia. Fort is because I feel like thematically, with the place being completely sovereign and being a place of battle, fort seems to be a fine title.
Let's hope those bugs get in their place (squished, and out of the code) to make room for alpha!