I think the point is market use. If he wasn’t marketing as “Jeep” then the law, as Alice In Wonderland as it sounds, would be that his commercial use of the name “could” come under challenge. (Whether to actually mount a challenge is at the discretion of the alleged infringee. Nobody, but Satan and some lawyers with heads up their rears, say that he “must.”) There was a brouhaha over a guy named Nissan who had an auto garage. The actual Nissan car company got a court order forbidding him to use that name on his garage. Mr. Nissan got very steamed over it, and a cat fight ensued which might still be going on. For me, if my name got encumbered that way, I’d just laugh and go on to something else. From my viewpoint God is in control and He is the “name above all names.” (If anyone has had the cheek to try to trademark “God” I haven’t seen it yet.)
The guy owned a bar, I think in Arizona, that was called “Jeep’s”. And Jeep was his real name. Like I said, if I remember correctly the bad PR caused Chrysler to drop the suit.