Combine a person leaning against a tree, and you get rest.
休 rest 휴
He is in need of rest.
그는 휴양이 필요하다.
Two Korean words,
휴식 休息 rest, relaxation
휴양 休養 rest, recuperation
The phrase for Be At Leisure (休閒) is comprised of Rest (休) + Leisure (閒)
Can you see how door and moon together make leisure? Makes sense that after work is done, at home at night, you can rest and relax.