당번 (tangbeon) means “person on duty”

More examples

내일 당번을 해서 일찍 와야 해요.nae il tang beo neul hae seo il jjik wa ya hae yo

I have to come early tomorrow because I'm on duty.

The person whose turn it is to handle a scheduled responsibility.

담당자tamdangja: A person who handles a particular responsibility on an ongoing basis.

한정된 기간 동안 정해진 일을 맡아 하는 차례의 사람han jeong doen ki gan tong an cheong hae jin i reul ma ta ha neun cha rye ui sa ram

Its Sino-Korean components express the idea of a duty coming to someone according to an assigned order.

The word fits a roster or timetable, so it helps describe organized turn-taking rather than a permanent job or role.