De acordo com a novelização de Matthew Stover, o nome "Vader" foi arrancado da própria Força (ênfase minha):
Darth Sidious laid a pale hand on Anakin's brow. "Then it is done. You are now one with the Order of the Dark Lords of the Sith. From this day forward, the truth of you, my apprentice, now and forevermore, will be Darth ..."
A pause; a questioning in the Force - An answer, dark as the gap between galaxies - He heard Sidious say it: his new name.
Vader.
Revenge of the Sith: The Official Novelization Chapter 17: "The Face of the Dark"
Mas não há indicação do que isso significa, ou porque a Força escolheu para ele.