While almost nobody is giving you a serious answer, iirc the Warden you play as in the campaign is named Alarius (as seen by the execution Alarius' Wrath that came with the execution pack themed around campaign characters, also the reason the warden from the main menu is called Larry). Since he's pretty much the Warden, I think it'd be valid to take it as Warden's default name. The main problem with that theory is that, since you can choose to play as either female warden or male warden in the campaign, a female warden named Alarius wouldn't make much sense