Is it ensure, insure, or assure?
early 1941, American English military slang, from G.P. "general purpose (car)," but influenced by Eugene the Jeep (who had extraordinary powers but only said "jeep"), from E.C. Segar's comic strip "Thimble Theater" (also home of Popeye the Sailor). Eugene the Jeep first appeared in the strip March 13, 1936. The vehicle was in development from 1940, and the Army planners' initial term for it was light reconnaissance and command car.