The story
- Proto-Indo-European*krewp-
- Proto-Indo-European*krewp-o-s
- Proto-Germanic*hreubazder.?
- Old High Germangrob
- Middle High Germangrob
- Germangrob
- GermanGrobianus
- GermanGrobian
- English todaygrobian
Borrowed from German Grobian (“brute”).
Etymology from Wiktionary, CC BY-SA 4.0.