Passage: Many explanations of the origin of the word jeep have proven difficult to verify. The most widely held theory is that the military designation GP (for Government Purposes or General Purpose) was slurred into the word Jeep in the same way that the contemporary HMMWV (for High-Mobility Multi-purpose Wheeled Vehicle) has become known as the Humvee. Joe Frazer, Willys-Overland President from 1939 to 1944, claimed to have coined the word jeep by slurring the initials G.P.  There are no contemporaneous uses of "GP" before later attempts to create a "backronym."

Question: GP is thought to be the original meaning of which word?
jeep