Originally posted by Lightsnake
Even when his Sithiness was public knowledge, there was never a Darth title until TPM
I am not saying that we do now owe Lucas for that. But it still fits in with the story. Knowledge of the Sith was almost completly lost and no one knew Palpatine's sith name. I do not think Palpatine would have told Mara Jade secrets like that. To him she was just an expendable pawn for him to use. So everyone assumed Darth was part of Vader's name. As for them not being able to find answers in the jedi archives when coruscant was eventualy retaken, Palpatine had already seen to it that the archives were destroyed. So instead they just refered to him as the name they knew him by.