Jeep as the name of the vehicle comes from:
1. An acronym of Just Enough Essential Parts.
2. A corruption of the initials GP, short for General Purpose (Vehicle).
3. "Jeepers Creepers," a euphemism for Jesus Christ, supposedly said by Maj. Gen. George Lynch when he took his first ride in the prototype.
4. The comic strip Thimble Theater, best known for Popeye the Sailor and Olive Oyl, which in 1936 introduced a character named Eugene the Jeep, a rodent-like character the size of a small dog whose only word was jeep!
Ain't saying. You'll have to go to the World Wide Words site to find out. If you are fascinated by words and grammar, you should love this site. It features Michael Quinuin writing "on international English from a British viewpoint." He's comprehensive without being pedantic or stuffy, and you're guaranteed to discover something you didn't already know.