Origin and development
The Oxford English Dictionary states that the origin of the current usage is unknown. There are two usually suggested possible origins: an earlier usage of gook, meaning prostitute; or goo-goo (also gugu), a term used by the US military to describe Filipinos. The prostitute usage is recorded in a slang dictionary published in 1893, which defined gook as "a low prostitute"; a similar meaning was recorded for gooh in 1859. This later came to imply a foolish or peculiar person. The goo-goo term, whose origins are similarly uncertain, was first used in 1899 by US troops in the Philippine–American War, although nigger was more prevalent.
Mencken reports the earliest use of the word gook: he wrote that US marines occupying Nicaragua in 1912 took to calling the natives gooks and that it had previously been a term for Filipinos. He further mentions that the natives of Costa Rica are sometimes called goo-goos. The first written use was in 1920 and mentions that the marines occupying Haiti used the term to refer to Haitians. US occupation troops in Korea after World War II called the Korans "gooks". Although mainly used to describe non-European foreigners, especially Asians, it has been used to describe foreigners in general, including Italians in 1944, Indians, Lebanese and Turks in the '70s, and Arabs in 1988.
It has been suggested that gook comes from the Korean word "국" (guk), meaning "country", "한국" (hanguk), meaning "Korea", or "미국" (miguk), meaning "America". For example, American soldiers might have heard locals saying miguk, referring to Americans, and misinterpreted this as "Me gook." These etymologies ignore the fact that there are many examples of the word's use that before the 1950s. So prevalent was the use of the word gook during the first months of the Korean War that US General Douglas MacArthur banned its use, for fear that Asians would become alienated to the United Nations Command because of the insult.
The term has been used by non-US militaries, notably the Rhodesian forces during the Rhodesian Bush War, where it was used interchangeably with terr to described the guerrillas, and by Australian forces during the Vietnam War.
In modern US usage, "gook" refers particularly to Communist soldiers during the Vietnam War. It is generally considered highly offensive. In a highly publicized incident, Senator John McCain used the word during the 2008 presidential campaign to refer to his former captors, then apologized to the Vietnamese community at large. "I hate the gooks. I will hate them as long as I live… I was referring to my prison guards and I will continue to refer to them in language that might offend." It was used in numerous movies and books depicting the Vietnam War.[nb 1]
- 1893 Slang and its Analogues. "GOOK, subs. (American). A low prostitute. For synonyms, see BARRACK HACK and TART."
- 1920 The Nation (magazine). The Haitians in whose service United States marines are presumably restoring peace and order in Haiti are nicknamed "Gooks".
- 1923 Le Slang. gook, a tramp: low.
- 1935 American Speech. Gook, anyone who speaks Spanish, particularly a Filipino.
- 1945 The American Language. "The Marines who occupied Nicaragua in 1912 took to calling the natives gooks, one of their names for Filipinos."
- 1947 New York Herald Tribune. The American troops...don’t like the Koreans – whom they prefer to call ‘Gooks’ – and, in the main, they don’t like Korea.
- 1950 The Potters of Firsk (story). Used multiple times by the Earthling supervisor to describe the indigenous population of planet Firsk.
- 1950 The Kansas City Star. "General MacArthur’s headquarters frowns on the practice of calling North Koreans "gooks." An article in the official magazine Tips says the person who uses the word is unwittingly guilty of giving aid and comfort to the enemy."
- 1960 Dictionary of American Slang. gook: Generically, a native of the Pacific islands, Africa, Japan, China, Korea or any European country except England; usually a brown-skinned or Oriental non-Christian.
- 1967 Doobie Doo (novel). "A gook in the purest sense is anybody what ain’t American."
- 1977 Rolling Thunder (film). Cliff: "Them gooks had no mercy".
- 2000 John McCain. Referred to his Vietnamese wartime experience, “I hate the gooks. I will hate them as long as I live… I was referring to my prison guards and I will continue to refer to them in language that might offend.” 
- 2004 Team America: World Police (film). "I was so sure the ultimate terrorist was Middle Eastern, but I didn't realize he was a goddamn Gook. I'll never be a racist again."
- 2008 Gran Torino (film). Walt Kowalski: "I'm no hero. I was just trying to get that babbling gook off my lawn!"
- "Gook: The Short History of an Americanism". Monthly Review. March 1992.
- Hughes, Geoffrey (2006). An Encyclopedia of Swearing. Routledge. pp. 207–8.
- Farmer, John S.; Henley, W. E. (1893). Slang and its Analogues, Past and Present. Harrison & Sons. p. 181.
- Lighter, Jonathan E. (1997). Random Historical Dictionary of American Slang. Random House.
- Paterson, Thomas; Merrill, Dennis (2009). Major Problems in American Foreign Relations, Volume I. Cengage Learning. p. 389.
- Unoki, Ko (2013). Mergers, Acquisitions and Global Empires. Routledge. p. 87.
- Dickson, Paul (2011). War Slang. p. 29. "Dickson cites Mencken's The American Language, Supplement 1 (1945)"
- Mencken, H. L. The American Language. p. 296.
- "The Conquest of Haiti". The Nation. 10 July 1920.
- "Gook". Rhetoric of Race. 2003.
- Cao, Lan; Novas, Himilce (1996). Everything You Need to Know About Asian-American History. Plume. p. 250. "Gook, the American racial epithet for all Asian Americans, is actually the Korean word for 'country."
- Lee, Robert G. (1999). Orientals: Asian Americans in Popular Culture. Temple University Press. "A bastardization of the Korean "Hanguk" (Korean), or Miguk (American)""
- Trans-Pacific Relations: America, Europe, and Asia in the Twentieth Century. Praeger. 2003. p. 117.
- "Use of Word “Gook” Is Opposed by MacArthur". The Kansas City Star. 12 September 1950.
- "Ironing the lawn in Salisbury, Rhodesia". The Guardian. 9 February 1980.
- Hyslop, Angus (1997). Jaws of the Lion: Rhodesia Before Zimbabwe. Lulu.com.
- Ma, Jason, "McCain Apologizes for ‘Gook’ Comment", Asiaweek,, February 24, 2000.
- Partridge, Eric; Beale, Paul (1984). A Dictionary of Slang and Unconventional English. p. 489. ""gook" entry references Manchon, J, Le Slang, Lexique de L'anglais Familier Et Vulgaire (1923)"
- Jack Vance (May 1950). "The Potters of Firsk". Astounding Science Fiction. "Audio from Dimension X radio show, event first occurs 05:17"
- "Soldiers revive "gook" as name for Korea reds". Los Angeles Times. 6 August 1950. p. 6.
- The Steel Helmet, 1951.
- (Wentworth, Harold and Stuart Berg Flexner, Dictionary of American Slang, (1960)).
- The Hook, 1963.
- Karp, Ivan, Doobie Doo 1967, p. 97.
- The War Veteran in Film. McFarland & Company. 2003. p. 44.
- "Memorable quotes for Team America: World Police" (2004).
- Heroes: What They Do and Why We Need Them. Oxford University Press. 2011. p. 87.