This is the 13200th most frequent Korean word.
뒤면
"뒤면" means "the back side" or "reverse side" in English.
뒤면 here refers to the reverse side or the area-behind something (in this case, the tree).
그는 나무 뒤면에 숨으려 했다.
He tried to hide behind the tree.
뒤면 is used to signify the back or unexposed side of the door.
문 뒤면이 아직 페인트칠이 되지 않았다.
The area behind the door has not been painted yet.
뒤면 here describes the 'back side' of the painting where something concealed is revealed.