What does G2 stand for?
G2 is the intelligence unit above the Regimental level [It was S2 at Regiment and Battalion]. G3 was Operations, G1 personnel, G4 Supply.
GI may have started as Government issue but there was also GI the barracks [clean it] or a GI shower given to guys who stunk because they didn’t shower in training, also everything is GI” for legit. Whatever, it meant OK.