Gook (/ˈɡuːk/ or /ˈɡʊk/) is a derogatory term for people of East and Southeast Asian descent...

When U.S. troops were stationed on the Korean Peninsula at the outbreak of the Korean War, so prevalent was the use of the word gook during the first few months of the war that U.S. General Douglas MacArthur banned its use, for fear that Asians would become alienated

https://en.wikipedia.org/wiki/Gook

"한국(韓國) 사람 (han'guk saram)"

" Korean (person)"

https://en.wiktionary.org/wiki/%ED%95%9C%EA%B5%AD_%EC%82%AC%EB%9E%8C

Koreans call each other gooks