What does Darth Vader

Origin of the name of Darth Vader

George Lucas

According to a New York Times article published in The Spokesman Review dated May 25, 1980s (the same article also tells of a trilogy of trilogies; see this question):

It took months for the intentionally mythical names of the Star Wars characters to develop. "Skywalker" was originally "Darklighter" and then "Starkill". "Darth Vader" was Lucas' careful mix of Deathwater and Darkfather. "Jedi" was chosen for its chivalrous echo of "Samurai", while "Obi-wan Kenobi" Lucas appears both ancient and hypnotically phonetically.

The article is largely an interview with George Lucas, so this information could have come straight from him. This is done in Researching American Culture Affirms: A Guide for Student Anthropologists, edited (1982) by Conrad Phillip Kottak (this seems to have also been published elsewhere in 1980):

It's easy to notice that Darth Vader is phonetically "dark father". In an interview with New York Times (May 18, 1980), just before the opening of The Empire Strikes Back , Lucas claimed he chose "Darth Vader" because it sounded like both "dark father" and "water of death".

Earlier speculation

An article in New Scientist (December 22-29, 1977) with the title Science in Folklore? Folklore in science? by Dr. Alan Dundes says:

It may or may not be relevant that the Archbird's name is Darth Vader, which strongly suggests death and father.

Literary onomastics studies , Volumes 5-7 (New York State University College, Brockport, New York State University College Brockport, Conference on Literary Onomastics) (1978) says:

Darth Vader's name combines elements that go as far as the sources of human emotion, because if I'm not mistaken, Darth is a portmanteau or a condensation of the words "dark", "earth" and "death". The response to the word "deficiency" is also remarkable.

Cinefantastique (Volumes 9-10) by Frederick S. Clarke (1979) claims:

Darth Vader's name is a cross between the symbols "dark" and "death" and the German word father [?], What Father means.

Science fiction studies - Issues 21-24 of Indiana State University. English Department (1980):

We now realize that Luke was fighting all along to kill his own father. The conscious suggestion of "Death Father" in the name of "Darth Vader" becomes transparent.