To untether something is to release it, to set it free. It's also the title for the newest trailer for id Software's RAGE - no doubt alluding to everyone's first real look at the game. One surprising thing about the trailer is the tone it sets, with light guitar musical track written by Mark Lanegan that makes the setting feel more western than apocalyptic. Of course the whole sheriff like character in a cowboy hat only adds to this motiff.
Of course what begins as almost calming and beautiful quickly comes to an end as the music revs up and the mutant blood begins to flow.