'Old World's mucky, violent and crowded, a-splitting right into bits of people a-hating each other and a-killing each other, no one happy till everyone's miserable. Least it was all those years ago.' Hildy describing Old World.
Old World was a planet (presumably Earth) that was inhabited by the human race. There was no Spackle and no Noise on it. People from Old World discover another planet capeable of supporting life - New World. At least two settler convoys have left Old World and landed on New World during the course of New World's history.