It's a simple word game but something that's easy to miss: the names of the android characters follow a pattern throughout the Alien series: in the original Alien, it's Ash (Ian Holm), in Aliens and Alien 3 it's Bishop (Lance Henriksen), in Alien: Resurrection it's Call (Winona Ryder), and in Prometheus, it's David (Michael Fassbender). So, that's A, B, C and D in chronological order (of release, not setting).