If anything Jeep on this list is backwards. It was originally a generic term for that military style vehicle made by various manufacturers. Then it became its own thing as the Jeep brand. But then Jeep further broadened their offerings ( Cherokee, Patriot, compass, etc) and the Jeep became a wrangler. But when I say I drive a Jeep, everyone assumes specifically a wrangler.
Well, the official name is G-Class (or G-Klasse in German). G-Wagen is a colloquial name. Wagen means vehicle in German, btw., where the G-Class isn’t known as G-Wagen at all.
The G is short for Geländewagen (off road vehicle) btw., so calling it G-Wagen is kinda like calling it an ATM-Machine.
Yeah, I thought the word Jeep originally came from the military initials GP - General Purpose vehicle. The generic term 4x4 (four by four) is pretty common in the UK.