Darth was a title given to certain Sith Lords which preceded either their chosen Sith name, or, in some cases, their birth name.
Many Sith Lords chose to add «Darth» to their name, so much so that the word is considered synonymous with the dark side of the Force in some circles. It was also taken to signify giving up one’s old life. Such examples are Anakin Skywalker becoming Darth Vader, or Jacen Solo becoming Darth Caedus. But the origins of the word are uncertain. It is often thought that «Darth» is merely a contraction of the title «Dark Lord of the Sith«, but there are theories that suggest a deeper interpretation.
Some historians suggest that «Darth» is actually a corruption of the Rakata word Daritha, meaning «emperor». Others note another Rakatan connection: the words for «triumph» or «conquest» in Rakatan is darr, and the word for «death» is tah, leading to the theory that «Darth» is derived from darr tah and therefore means «triumph over death» or «immortal».[7] Given the Sith obsession with discovering the means to achieve immortality, this idea is not entirely without merit, at least on the surface. But others point out that the true meaning of darr tah is «conquest through death,» meaning the conquest of one’s enemies.[1]
Ultimately, the flaw in such theories involving a Rakatan origin is that, even if they are accurate, they cannot spring specifically from Revan or Malak’s re-discovery of the Rakata and the Star Forge. Five years prior to their emergence as Sith Lords (3964 BBY), the title «Darth» was already well known by the Jedi in connection to the Sith, which is why Padawan Zayne Carrick could call Jarael «Darth Sunshine.» In addition, Haazen claimed that if he were to take a name like the Sith of old, it would be «Darth Hayze,» all but asserting that the title Darth was around prior to Revan and Malak’s discovery. There is still the possibility that one of the Rakatan theories could be correct, since the ancient Sith homeworld of Korriban had once been occupied by the Rakata (circa 28,000 BBY), which is one way either the Daritha or darr tah term could have entered the ancient Sith language. Darth Andeddu lived during the time of the old Sith Empire (6900 BBY to 5000 BBY), early enough for his holocron to come into the possession of the fallen Jedi Freedon Nadd. He was known for experiments into eternal life, a possible link to the Rakatan term.
But even if the Rakatan connection proves to have some validity, numerous other cultures make similar claims to the etymology of the title, so for the present, there is no definitive answer as to what the term «Darth» truly means.