動作本身
這一組就是核心畫面：小、重複、不自覺的動作，一個當動詞用，一個把它數成一次一次。
verb · B2
To keep making small restless movements with your hands, feet, or body, especially when you are bored, nervous, or waiting for something.
坐不住地動來動去
核心畫面
A person sitting still on the outside and not still at all: a foot swinging, a pen turning, a sleeve being twisted, a body shifting in a chair. Every movement is small, every movement repeats, and almost none of them are planned — the hands keep going while the mind waits. Hold that picture and the rest of the word follows, because English simply gives the same name to the movement, to the person who makes it, and to the little object made to receive it.
可以想成一個人表面上坐著，其實一刻也沒停：腳在晃、筆在轉、袖口被扭來扭去、身體在椅子上換來換去。每個動作都很小，每個…更多收起
可以想成一個人表面上坐著，其實一刻也沒停：腳在晃、筆在轉、袖口被扭來扭去、身體在椅子上換來換去。每個動作都很小，每個動作都一直重複，而且幾乎都不是刻意的——心在等，手自己在動。這個畫面抓住了，其他用法就順著出來了。因為英文乾脆把同一個名字給了三樣東西：那個動作、做這個動作的人，還有專門做來讓手玩的那個小東西。From the word’s history
The source derives fidget from fidge, meaning to fidget, plus a frequentative ending, possibly going back through Middle English to Old English -ettan.
來源說 fidget 來自舊字 fidge（動來動去），加上一個表示「一再重複」的字尾，這個字尾可能一路追到古英文的 -ettan。那個「一再重複」正好是這個字的關鍵：重點從來不是動了一下，而是停不下來地一直動。
Wiktionary entry supplied in packet (kaikki:3f6f69a190036ae4:863321525)
Two branches
動作連上的人和東西
英文把動作的名字直接借出去：借給一直做這個動作的人，也借給專門讓人做這個動作的小物。
noun · B2
A person who cannot sit or stand still and keeps making small restless movements. The source marks it informal, and it is usually said in a light way about someone you know well.
坐不住的人