Picture a number that will not sit still: ten, nine, eight — each one smaller than the last, each one bringing a fixed moment closer. Countdown can be thought of as the stretch of time those shrinking numbers cover. Nothing has happened yet; that is the point. The whole feeling of the word lives in the gap between the first number and zero, and in knowing exactly where that gap ends.
countdown 可以想成一串停不下來的數字：10、9、8，一個比一個小。每少一個數，那一刻就近一點。這個字指的不是零那一秒，而是數字在走的那一整段時間。事情都還沒發生，這正是重點。整個字的味道就住在「開頭那個數」和「零」之間，而且你清楚知道盡頭在哪裡。
From the word’s history
The supplied Wiktionary entry gives the formation directly: countdown is count + down — counting that goes downwards, towards zero.
手上的 Wiktionary 資料直接寫著 count + down：往下數的數。數到最底就是零，也就是事情發生的那一刻，這跟今天三個用法的畫面都對得上。
Wiktionary entry for countdown, kaikki extract source_ref kaikki:3f6f69a190036ae4:328995188:27970 — etymology_text: “From count + down.”
登入就可以看每一支怎麼連回核心畫面。