We chose the name railGun 3D because of how we intend to accelerate development of 3D games on the web, and we will do this using new technology.
Wikipedia article on rail guns: http://en.wikipedia.org/wiki/Railgun
While our market is gaming, our target audience are developers, not the end customers, hence the lean toward more serious designs. These people will typically be gamers themselves, but are looking for serious tools for development.
We are focused on 3D games, so it's possible that should be reflected in the design, but it is not critical.
We think we want just the G capitalized in railGun, but are not settled on that yet, so designs with different capitalization (Railgun, RailGun, railgun, RAILGUN) are all permissible.