What was the founder’s first ‘working name’ for Minecraft?

The wikipedia article for the game says that before Notch had settled on “Minecraft” for the name of his game, he had considered many other working titles, including “Cave Game”, “Mnemonic”, “Rock Simulator” and “Castle Game”. He didn’t want there to be speculation about what new game he was developing. On 10 September 2009 it was announced that it would instead use the name Minecraft. This is because when we first people started playing a pre-release version of this video game at PAX East in March 2009 they kept asking him what the title of his new game was called. And so Markus began telling them ‘It shall be called Minecraft,’ which became an inside joke.