I thought it sounded peculiar.That is a mistranslation. The wombat family is also known as Plumpbeutler in Germany, which means as much as plump (as in lumpy) marsupials.
This is the passage from the link:
Wegen ihres gedrungenen Aussehens, das die Verwandtschaft mit den Kängurus kaum erahnen lässt, tragen Wombats in unserer Sprache den wenig schmeichelhaften Namen Plumpbeutler – mit den kurzen Beinen und dem Stummelschwänzchen sehen sie ein bisschen aus wie kleine Bären.
When I put the whole thing into Google translate it came up with the word "squatters" rather than "slugs". When I tried just the word Plumpbeutler by itself the computer just scratched its head and said Plumpbeutler back.