The generally accepted meaning/romanization for デジョン is "Dezone", at least that was the accepted one in XI. Warp II was pretty much always shortened as D2 and whenever someone wondered why that was the explanation given.

Semi-related question, is it possible to install the FFXIV client in 2 languages (EN and JP) on the same system? At least unlike XI you don't need to jump through hoops (and use software barred by the ToS) just to type in Japanese using the EN client, but being able to play with the interface/logs in Japanese would be a good way to force myself to have regular practice.