OOOs is pronounced OWES, i get it, with the Greed theme.
The name refers to several things at once, like an infinity symbol with an extra O (episode 2) or the three medals in his belt. "Owes" is not one of those references, but it's a cute idea!
darksenshi, people always seem to hate the latest Rider design when it's shown in promotional material and make all sorts of inferences about the show from the tidbits of knowledge, but once they give it a shot are pleasantly surprised. It's happened ever since Hibiki, at least! Surprise, surprise, you might just like OOO.