Gung ho is an anglicised pronunciation of "gōng hé" (工合), which is additionally at times anglicised as "kung ho". "Gōng hé" is a shortened version of the term "gōngyè hézuòshè" (工業合作社) or Chinese Industrial Cooperatives, which was abbreviated as INDUSCO in English.
The two Chinese characters "gōng" and "hé" are translatable individually as "work" and "together".
The linguist Albert Moe studied both the origin and the usage in English. He concludes that the term is an "Americanism that's derived from the Chinese, but its several accepted American meanings have no resemblance whatsoever to the recognised meaning in the original language" and that its "various linguistic uses, as they have developed in the United States, have been peculiar to American speech." In Chinese, concludes Moe, "this is neither a slogan nor a battle cry; it is only a name for an organization."
The term was picked up by United States Marine Corps Major Evans Carlson from his New Zealand friend, Rewi Alley, one of the founders of the Chinese Industrial Cooperatives. Carlson explained in a 1943 interview: "I was trying to build up the same sort of working spirit I had seen in China where all the soldiers dedicated themselves to one idea and worked together to put that idea over. I told the boys about it again and again. I told them of the motto of the Chinese Cooperatives, Gung Ho. It means Work Together-Work in Harmony...."
Later Carlson used gung ho throughout his (unconventional) command of the 2nd Marine Raider Battalion. From there, it spread throughout the U.S. Marine Corps (hence the association between the two), where it was used as an expression of spirit and into American society as a whole when the phrase became the title of a 1943 war film, Gung Ho!, about the second Raider Battalion's raid on Makin Island in 1942.