Jeep is an automobile marque of Chrysler. It is the oldest off-road vehicle brand, with Land Rover coming in second. The original vehicle which first appeared as the prototype Bantam BRC became the primary light 4-wheel-drive vehicle of the US Army and allies during the World War II and postwar period. Many vehicles serving similar military and civilian roles have since been created by many nations. Jeeps were also used by the U.S. Postal Service in the 20th century for mail services. There are many explanations of the origin of the word "jeep," all of which have proven difficult to verify.... Probably the most popular notion holds that the vehicle bore the designation "GP" , which was phonetically slurred into the word jeep. However, R. Lee Ermey, on his television series Mail Call, disputes this, saying that the vehicle was designed for specific duties, was never referred to as "General Purpose," and that the name may have been derived from Ford's nomenclature referring to the vehicle as GP wheelbase.