I always thought the Sith names (from the movies) are based on what Palpatine uses the particular Dark Lord for, or what they do
(You may need to scroll a bit for more applicable definitions, particularly "Maul" and "Tyrannus")
Darth Maul: (maul
) seems pretty straightforward. He just attacks. He's like a hunting dog.
Darth Tyrranus: (Tyrranus
) Dooku is a Count
, which pretty much makes the name relevant. But also, Palpatine uses Dooku to gain absolute power. So perhaps the name is more relevant to how Palpatine uses his pawn.
Darth Vader: (invader
) We know that Anakin helps the Emperor "hunt down and destroy" the Jedi. The name seems applicable here too. Palpatine, it seems, uses Anakin to conquer or invade the Jedi Order.
Darth Sidious: (insidious
) This also seems very straight forward. I feel like Darth Sidious isn't even Palpatine's true identity, but rather just a persona he uses as a means to an end. Palpatine is Palpatine's persona. He uses
the Darth Sidious persona just as he used Maul, Tyrannus and Vader. Also, in the old Star Wars
books, the text always mentioned the Old Republic rotting from the inside out. Palpatine is obviously the cause of this "insidious" disease...
Anyways, that's my theory. Maybe it just means "Larry" or something.