This is in the storyline: >In 1988, a brand new deep sleep cell was released, compatible with all popular 16 bit computers. So I've assumed from the start tha

This is in the storyline: >In 1988, a brand new deep sleep cell was released, compatible with all popular 16 bit computers. So I've assumed from the start that the D is for Deep, because the whole story is about this deep sleep stuff. But yeah, that's really just speculation. I don't think there's any official answer to it.