那根讓東西轉的銷
核心畫面本身，也是這個字最早的樣子：一個零件。
noun · C1
A small part that joins two things and lets one of them turn round freely without the other one turning.
轉軸；旋轉接頭
核心畫面
One way to hold swivel: a pin stuck through two things so that one of them can spin and the other stays put. Everything about the word comes back to that pin. The place never changes; only the facing does. Put the pin under a chair and the chair swivels. Put it in a dog lead and the lead never twists. Imagine the pin inside a person's waist or neck, and you get someone swivelling round without taking a step.
swivel 的畫面可以想成一根銷穿過兩個東西：一邊可以轉，另一邊留在原地。這個字的每個用法都回到那根銷。位置從不改…更多收起
swivel 的畫面可以想成一根銷穿過兩個東西：一邊可以轉，另一邊留在原地。這個字的每個用法都回到那根銷。位置從不改變，改變的只有方向。銷裝在椅子下面，椅子就會轉。銷裝在狗鍊尾端，繩子就不會纏。把那根銷想像在一個人的腰或脖子裡，就是一個人腳不動、整個上半身轉過來的樣子。From the word’s history
Wiktionary derives swivel from a form of Old English swifan, to revolve, plus -el, an instrumental suffix — literally the little thing that turns. That is why the part, not the movement, sits at the centre here.
來源把 swivel 追到古英語 swīfan（旋轉）加上表示器具的字尾 -el，字面就是「讓東西轉的小玩意」。所以這裡把零件放在中心，而不是把動作放在中心。
Wiktionary entry for swivel: From Middle English swyvel, from a derivative of Old English swifan (to revolve), + -el, an instrumental suffix — as supplied in the evidence packet
Two branches
像裝了那根銷一樣地轉
把零件的功能借給人和身體：位置不動，只有方向換了。
verb · B2
To turn quickly to face a different direction while staying in the same place, or to turn something in this way.
（原地）轉動、轉身