User blog comment:FairyRaven/Fairy Tail Chapter 357: The Nine Demon Gates, Review and Commentary/@comment-7397924-20131025101743/@comment-7418318-20131025105409

Maybe he just didn't want to give away his name to them.

Or tempesta could be his title/second name/book name/whatever (the "Absolute Zero", "of the shell", "of the darkness", ect. part of the other gate's names) with him just lacking the "first name".