The expression 'NG' originally started in the Japanese broadcasting industry as a shortened term for 'No Good.' It then came over to Korea, where it became widely used in broadcasting and film.

Korean variety shows often create big laughs by compiling and showing the cast's funny mistakes or NG scenes. As such, it's best used not for serious failures, but for lighthearted, humorous situations or to cutely express your own small blunders.