Picture a full name as three slots in a row. The first slot is the name people call you, the last slot is the family you come from, and the middle slot holds a name that rides along quietly — usually shrunk to a single letter, brought out in full only on official papers. Because that middle slot is printed into who you are and never comes off, English also borrows it for a joke: name a quality, call it your middle name, and you are saying the quality is stamped into you.
Two branches
名字裡的中間那一格
這一家就是核心畫面的字面版本：全名三格，講的正是中間那格。
noun · A2
The name that sits between your first name and your family name. Many people in English-speaking countries have one, and it is often shortened to a single letter or written out only on official papers.
中間名
把特質寫進名字裡的玩笑話
中間那一格是印在名字裡、拿不掉的東西。把一個特質放進那一格，就等於說這個特質跟名字一樣長在身上。
noun · B2
Used to joke that a quality belongs to someone so completely that it might as well be part of their name. You name the quality, then say it is your middle name, or someone else's.
是我的代名詞