Picture a lock that has gone dead. The bolt is all the way out, the key will not turn, and the door will neither open nor close. Nothing is broken and nothing is missing — the parts are simply pressed against each other so that nothing can move. Every use of this word is that same stuck bolt, borrowed for people, for talks, or for machines.
可以想成一把卡死的鎖：鎖舌整個推出去了，鑰匙轉不動，門既開不了也關不上。畫面的重點不是「壞掉」，也不是「少了零件」，而是兩邊頂在一起，誰都動不了。這個字後來的每一種用法，都是把這根卡死的鎖舌借去講別的東西——人、談判，或機器。
From the word’s history
The word is simply dead plus lock. English uses dead in this way in several places — a dead stop, a dead end — to mean that something has no give left in it at all.
這個字就是 dead 加 lock。英文常這樣用 dead 表示「完全沒有轉圜」，像 dead stop、dead end，這裡的 dead 也是同一個意思。
Wiktionary etymology supplied in this evidence packet (kaikki:3f6f69a190036ae4): "From dead + lock."
登入就可以看每一支怎麼連回核心畫面。