Green’s Dictionary of Slang

gung-ho adj.

also gungy
[Chinese keng ho, awe-inspiring (lit. ‘more fiery’). The term was initially popularized as the motto of the US Marine Corps Second Raider Battalion, introduced there in 1942 by Lieutenant Colonel Evans F. Carlson]

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

[US]C.R. Bond 12 Mar. in A Flying Tiger’s Diary (1984) 127: The tiger spirit of a gung-ho American fighter pilot.
[WI] ‘Matty Walla-Lef’ in T. Murray Folk Songs of Jamaica 50: Matty run a mile an’ a half, eena gun-go walk (Mm Mm).
[US](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.
[US](con. 1958) R. Farina Been Down So Long (1972) 166: I wrote the letter, right? Rest is up to all the gungho troopers.
[US]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?’.
[US](con. c.1970) G. Hasford Short Timers (1985) 161: You be gung ho, Mother. You give the orders.
[US]C. Hiaasen Skin Tight 111: Garcìa was having a ball, acting so damn gung ho.
[US]T. Jones Pugilist at Rest 11: When did you get so gung-ho, man?
[US]P. Beatty Tuff 30: Even after six months she was still a gung-ho serf in the Burger King’s fast-food realm.
[US]UGK ‘Chrome Plated Woman’ [lyrics] These niggaz schemin on my young hoe / Niggaz so gung-ho.
[US]‘Harry Brandt’ Whites 2: There were gung ho detectives out there, even on the lobster shift, but Billy was not one of them.