G.I. is a noun used to describe the soldiers of the United States Army and airmen of the United States Army Air Forces—and for U.S. Marines and sailors—and also for general items of their equipment. The term G.I. has been used as an initialism of “Government Issue” or “General Issue”, but it originally referred to “galvanized iron“, as used by the logistics services of the United States Armed Forces. The letters “G.I.” were used to denote equipment made from galvanized iron, such as metal trash cans, in U.S. Army inventories and supply records.
Additional Information: en.wikipedia.org/wiki/G.I._%28military%29