GIyoudaoicibaDictYouDict[GI 词源字典]
GI: [20] GI originated, around the beginning of the 20th century, as a US abbreviation of galvanized iron. It was soon in common use in the military, in contexts such as GI can, and the idea seems to have got about that it stood for not galvanized iron but government issue. This misconception propelled it into such combinations as GI shoe, GI soap and (facetiously) GI soldier. By the 1930s this had been shortened to simply GI, designating an enlisted man in the US Army.
[GI etymology, GI origin, 英语词源]