Jajangmyeon dates back to 1905, when it first appeared in Gonghwachun (공화춘; 共和春), a restaurant in Incheon Chinatown run by an immigrant from the Shandong Province of China. The restaurant is now the Jjajangmyeon Museum.
Jajang (자장; alternately spelled jjajang 짜장) is derived from the Chinese word zhájiàng (炸酱), which means "fried sauce". Myeon (면) means "noodles". The Chinese characters are pronounced jak (작; 炸) and jang (장; 醬) in Korean, but the noodle dish is called jajangmyeon, not jakjangmyeon, because its origin is not the Sino-Korean word, but a transliteration of the Chinese pronunciation.
Source : @wikipedia