The family name Kwak is written with a hanja meaning "city walls" (郭; 둘레 곽; dulle gwak; also called 외성 곽, oeseong gwak).
The same character is also used to write the family names Guō in Mandarin Chinese, Kwok in Cantonese, Kaku in Japanese, and Quach in Vietnamese.
The 2000 South Korean census found a total of 187,322 people and 58,396 households with this family name.
[1] They identified with a number of different bon-gwan (seat of a clan lineage, for example the residence of an ancestor from whom the clan claims descent): In a study by the National Institute of the Korean Language based on 2007 application data for South Korean passports, it was found that 75.4% of people with this family name spelled it in Latin letters as Kwak in their passports, while 14.4% spelled it in Revised Romanization as Gwak, and 5% spelled it Kwag.
Rarer alternative spellings (the remaining 5.2%) included Kwack, Gak, Guak, Kwack, Gwag, Kag, Kawk, Koag, Koak, Kweak, and Kwug.