Picture a chair with nobody on it. To occupy something is to come in and take up the space and hold it; un- lifts that person straight out again. What is left is a place waiting for someone: the seat is still there, the furniture is still there, only the person is missing. Stretch that empty place in two directions and you have the whole word — shrink it to one chair or grow it to a whole country, and turn the place into a person's time, where nothing has come in to fill the hours either.
From the word’s history
Middle English unoccupied, formed from un- plus occupied.
中古英語就有 unoccupied 這個形式，結構是 un-（沒有）加 occupied（被佔用的）。這條線索跟今天的用法完全對得上：先有「被佔住」的畫面，再用 un- 把它取消掉。
Wiktionary entry for unoccupied (kaikki:3f6f69a190036ae4:1292894926:18796): From Middle English unoccupied; equivalent to un- + occupied.
登入就可以看每一支怎麼連回核心畫面。