Darth

"Henceforth, you shall be known as Darth&hellip; Vader."

- Darth Sidious, upon making Anakin Skywalker his new apprentice

Darth was a title given to the Dark Lords of the Sith Order, which preceded a moniker different from the birth name. It roughly translated to "Dark Lord." The Sith names of Sheev Palpatine, Count Dooku, and Anakin Skywalker were Darth Sidious, Darth Tyranus, and Darth Vader, respectively.

History
The title was already in use about a millennium before the Clone Wars, when Darth Bane established the Rule of Two. In at least two known cases (that of Count Dooku and Anakin Skywalker), the Darth title and the accompanying moniker were bestowed onto the Sith apprentice by the master.

The Jedi Master Obi-Wan Kenobi once used "Darth" as a form of address when talking to Darth Vader. Imperial officers typically addressed Vader as "Lord Vader".

Non-Canon Appearances

 * Star Wars Epic Yarns: A New Hope
 * Star Wars Epic Yarns: The Empire Strikes Back
 * Star Wars Epic Yarns: Return of the Jedi
 * LEGO Star Wars: Droid Tales Episodes I-III