When Anakin turned to the Dark Side Darth Sidious obviously saw fit to give him a new name:
PALPATINE: Henceforth you shall be known as Darth...Vader.
ANAKIN: Thank you, my master.
I've seen the question that's already been asked about the out-of-universe reason why George Lucas landed on the name Vader. I'm interested in whether there's an in-universe explanation for why Palpatine decided to call him what he did.
Was it just a random name plucked out of thin air? Did Palpatine pick it because he knew that Padmé was shortly due to give birth? Is there any preexisting connection between the name 'Vader' and the Dark Side of the Force?