True, but Vader's name can still be explained with the use of English terms like Invader and all. Darth Oorlog of Darth Patatzaak can't be
Just like you said, they should be based on real-world stuff, not a random foreign term.
If Star Wars would be a German or Dutch only thing and English wasn't the nr1. language around, Darth Oorlog would be something like Darth War and Darth Smile, in comparison. Or Darth Pedestrian. Just plain stupid
Although the Vader/Father part IS quit strange...because it actually fits.