I kind of dig the idea of a double meaning: 1. Chosen from amongst the dead to be Guardians; and 2. Chosen by someone/something (e.g. The Darkness or even...The Traveller) to be dead in the first place. After all, someone/something had to kill us all when we were in our prime (haven't met any old/infirm or child Guardians). I don't think we were killed by the measles or old age. As such, whatever killed us "chose" us to be dead. And what would be really creepy is if whatever chose us to be dead also chose us to be Guardians (i.e. The Traveller).