Green’s Dictionary of Slang

(orig. US) often of soldiers or sportspeople, enthusiastic, usu. aggressively so; thus as v., to do something in an aggressive manner.

1942		C.R. Bond 12 Mar. in A Flying Tiger’s Diary (1984) 127: The tiger spirit of a gung-ho American fighter pilot.
1951		‘Matty Walla-Lef’ in T. Murray Folk Songs of Jamaica 50: Matty run a mile an’ a half, eena gun-go walk (Mm Mm).
1958		(con. 1950) E. Frankel Band of Brothers 1: You and the captain [...] Real gung-ho gyrenes. [Ibid.] 88: We’re going to have to gung-ho up there.
1966		(con. 1958) R. Farina Been Down So Long (1972) 166: I wrote the letter, right? Rest is up to all the gungho troopers.
1978		J. Webb Fields of Fire (1980) 335: ‘They tried to make me [...] a battalion supply officer. But I told ’em I needed the bush, man.’ Bagger squinted, taken aback. ‘When did you get so gungy, Lieutenant?’.
1979		(con. c.1970) G. Hasford Short Timers (1985) 161: You be gung ho, Mother. You give the orders.
1989		C. Hiaasen Skin Tight 111: Garcìa was having a ball, acting so damn gung ho.
1993		T. Jones Pugilist at Rest 11: When did you get so gung-ho, man?
2000		P. Beatty Tuff 30: Even after six months she was still a gung-ho serf in the Burger King’s fast-food realm.
2006		B. Matthews Intractable [ebook] [A] couple of the younger gung-ho screws who wanted to make a name for themselves by pinching me.
2007		UGK ‘Chrome Plated Woman’ 🎵 These niggaz schemin on my young hoe / Niggaz so gung-ho.
2015		‘Harry Brandt’ Whites 2: There were gung ho detectives out there, even on the lobster shift, but Billy was not one of them.