One way to hold spanner: a piece of shaped metal in your hand that takes hold of a nut and turns it. It has to grip before it can turn, and it is the grip that does the work.
The supplied Wiktionary entry gives spanner as span + -er, that is, the thing that spans. That fits a tool that reaches across a nut and takes hold of both sides of it.
封包裡的 Wiktionary 說 spanner 來自 span 加上 -er，字面是「做跨越動作的那個東西」。這條線索對得上工具的樣子：它跨過螺帽，從兩邊把它扣住。所以先想「跨過去、扣住」，再想「轉」，這支工具的畫面就完整了。
Wiktionary entry supplied in packet (source_ref kaikki:3f6f69a190036ae4:409867841): "From span + -er."
Three branches
手裡那支會咬住螺帽的工具
這一家就是核心畫面本身，只是英式和美式各自圈出的範圍不一樣大。
noun · B1
A metal hand tool that fits onto a nut or the head of a bolt so that you can turn it, either to tighten it or to undo it. British, Irish and other Commonwealth English usually say spanner here; American English usually says wrench.
扳手
掉進機器裡、把事情卡住的那支
同一支金屬工具，位置換了：不在手上，而是掉進齒輪裡。它原本用來讓機器轉得動，現在讓機器動不了。
noun · B2
To do something unexpected that stops a plan or a process from going smoothly, or stops it from working at all. The verb can be put or throw.
打亂計畫
拿工具的名字叫人
英文常拿硬邦邦的物件來叫人，這裡就是其中一個。它跟核心畫面的連結是鬆的，當成同一個字的另一種用法記就好，不必硬掰成比喻。
noun · C1
A mildly rude British and Irish word for someone who is being silly or who has just made a stupid mistake, often a mistake with words. It is mostly used about yourself or about a close friend, as a light insult.
呆瓜（輕度罵人）