攻不破的承諾與證據
把那件鐵衣從船上脫下來，蓋到看不見的東西上：一份保證、一紙合約、一個不在場證明。防的不再是砲彈，而是爭辯和推託。
adjective · C1
An ironclad agreement, rule, promise or piece of proof is so strong and so certain that nobody can change it, get around it or argue against it.
牢不可破的
核心畫面
The word says its own picture out loud: iron plus clad, something wearing a coat of iron. Start with a wooden ship in the 1860s with sheets of iron bolted over its sides. Shot after shot hits it and nothing gets through. Now take the coat off the ship and lay it over a promise, a contract, an alibi: the same idea, that there is no soft spot anywhere on the outside and nothing can get in. Each meaning in this entry is that coat of iron on a different thing.
這個字自己把畫面說出來了：iron（鐵）加上 clad（披著），也就是「穿著一件鐵衣」。先看一八六零年代的木船，側面…更多收起
這個字自己把畫面說出來了：iron（鐵）加上 clad（披著），也就是「穿著一件鐵衣」。先看一八六零年代的木船，側面釘上一塊塊鐵板。一發一發打上去，都穿不進來。接著把那件鐵衣從船上脫下來，蓋到一份承諾、一紙合約、一個不在場證明上面：概念完全一樣，外面找不到一處軟的，什麼都進不來。這個條目裡的每一個意思，都是同一件鐵衣披在不同的東西上。From the word’s history
From iron plus clad, where clad goes back through Middle English to Old English for clothing something. So the word is literally iron-dressed, which is why both the ship and the promise make sense under one image.
由 iron（鐵）加上 clad 組成；clad 經中古英文上溯到古英文表示「給…穿衣服」的字。所以整個字字面上就是「被鐵穿上的」。船和承諾能共用一個畫面，原因就在這裡。
Wiktionary entry for ironclad, etymology tree iron + clad, source_ref kaikki:3f6f69a190036ae4:1115046431:17758 (packet evidence)
From the picture
Also in this word
adjective · C1
Covered on the outside with plates of iron or steel for protection, especially an old warship.
包鐵的