現代法律與金融：把確定交出去
這一群是今天真正會用到的三個用法：確定被做成一個人、一個動作、一筆錢。
noun · C1
A person or a company that promises to pay a debt, or to make sure someone comes to court, if the person who really owes it fails to do so.
保證人
核心畫面
One way to hold this word: being sure is a feeling inside your head, and nobody else can see it. `Surety` is what happens when that feeling is pushed out into the world so other people can rely on it too. A court cannot see that a person will come back, so it takes money and holds it — now the certainty is sitting in a drawer. A bank cannot see that a loan will be repaid, so it takes a second name — now the certainty has a face and an address. Every meaning of the word is certainty made into something you can hand over: a sum, a signature, a person standing behind you.
可以想成：「確定」本來只長在你自己腦袋裡，別人看不到。surety 就是把這份確定推到外面，變成別人也能依靠的東西。…更多收起
可以想成：「確定」本來只長在你自己腦袋裡，別人看不到。surety 就是把這份確定推到外面，變成別人也能依靠的東西。法院看不出這個人會不會回來，所以先收一筆錢押著——確定於是躺在抽屜裡。銀行看不出這筆錢會不會還，所以要第二個名字——確定於是有了臉、有了住址。這個字的每一個用法，都是把確定做成一樣交得出去的東西：一筆錢、一個簽名、一個站在你後面的人。From the word’s history
Wiktionary traces surety through Middle English surete and Anglo-Norman seurté to Latin securitas, and notes it is equivalent to sure + -ty and a doublet of security. It records the guarantee, pledge sense from the early 1300s, certainty from the late 1300s, and one who undertakes to pay if another does not from the early 1400s. So the word really did travel from being sure, to the thing that makes you sure, to the person who carries the risk.
Wiktionary 記載：surety 經由中古英文 surete、盎格魯-諾曼語 seurté 上溯到拉丁文 securitas，等於 sure 加名詞字尾 -ty，並且和 security 是雙生字。它也標出年代——1300 年代初是「保證、承諾」，1300 年代末是「確定」，1400 年代初才出現「別人不付時代為支付的人」。所以這個字確實一路從「確定」，走到「讓人確定的東西」，再走到「扛責任的那個人」。
Wiktionary entry `surety` (noun), etymology text supplied in evidence packet (Middle English surete < Anglo-Norman seurté < Latin securitas; sure + -ty; doublet of security; dated sense history).
Two branches
較舊的一層：確定本身，以及確定的依據
這一群是這個字還沒變成錢和人以前的樣子。現在主要是讀舊書時會遇到，但它把整個字的來路交代清楚了。
noun · C2
Certainty; the state of being completely sure. This use is old, and today you meet it mainly in older books and in the set phrase `of a surety`, which means `certainly`.
確定；確實