Birth by Sleep Terra's real name.

I bet that if we pester Nomura with many, many, many, many, many, many e-mails asking for Terras real name, he will give in.

Seriously, just wait and it will probably be very important because it could be that he changed his name to forget about his past, etc. Just wait and all will be revealed soon enough. (I have to stop being over philosophica in the way I type things. >.<)

 

Late in response to this but

*COUGH* CID *COUGH*

 

His name probably IS Terra, or, like Ven, it's Terra-something longer.

 

When you look at that though doesn't that go with Terra-Riku=Earth, Aqua-Kairi=Water, Ven-Sora= Wind?

 

No guys, it's Tella. That way my Axel=Terra theory comes true. t e l l a/ remove an "l" and a "t"/ e l a/ and an "x"/ e l a x/ a x e l. See. Axel. I figured it out!

Isn't that beautiful!?

 

Terra's name doesn't mean 'unknown'. Terra means 'earth' in Spanish and Latin. I'm not sure where you ever heard it means 'unknown'. I'm pretty sure that Terra's name is simply Terra and he probably has a last name. The only one in the game that appears to have an abbreviated name is Ven and we know his full name as well and is Ventus.

All of their names, as others have said, correspond with the elements, just as Sora, Riku and Kairi's names do.

Sora (sky) = Ventus (Wind)
Riku (land) = Terra (earth)
Kairi (sea) = Aqua (water).