I'm very likely completely wrong, but didn't some people merely latinize the spelling rather than translate, e.g. most people seem to believe that Clavius' original name was Clau or Klau rather than Schlüssel for key (Latin clavis).

Some Latinized the name. There's a famous German jurisprudentist whose name is Heineccius, which was probably just Heinecke with -ius. Not only Latin, but Greek, too; there are names like Neander (a couple of Germans, a theologian and a philologist) which is the Greek translation of German Neumann, and Melanchthon was originally called Schwarzerd. Katz is a common Ashkenazi surname, but it has nothing to do with German Katz 'cat', but rather is a Hebrew acronym כ״ץ (K.Tz.), short for kohen tzadeq 'righteous priest'. So, it depends, hence my slight qualification. I did a minimal googling and that's the best solution I came up with. Perhaps Branny knows if there is a Dutch word pretor that means something.

Ceci n'est pas un seing.