As everyone has said over and over, Tee-dus comes from Kingdom Hearts. Given that's an official pronuncition, that is the TRUE pronunciation.

Like I said before, I originally said Tie-dus as well, as it makes sense. However, when the makers of the game say it one way, then that is the correct way, that's the way it's intended to be said.

I've never heard of anyone actually named Tie-dus, and I'm pretty sure it isnt a real name at all, though I cant be sure.