You can think of loopy as a line that will not go straight. Instead of running from one point to the next, it curls back on itself again and again: rollercoaster track turning a full circle, handwriting full of round curls, a mountain road folding back six times. Hold that curling line, then put it inside someone's head, and most of the other uses of the word open up.
loopy 的核心畫面可以想成一條不肯走直線的線。它不是從 A 直接到 B，而是一路捲、一路繞，甚至繞回自己身上。雲霄飛車的軌道翻整整一圈、字跡圓圓捲捲、山路一彎再彎，都是這條線。把這條繞圈的線放進腦袋裡，這個字的其他用法差不多就通了：想法接不上直線，就是怪怪的、暈暈的、快撐不住了。
From the word’s history
Wiktionary gives loopy as loop + -y. The literal shape sense sits right on that build, and the head senses read as the same picture moved inside a person.
Wiktionary 記載 loopy 來自 loop（圈圈）加上 -y（有…的樣子）。形狀上的意思最貼近這個字面組合；講人、講腦袋的用法，讀起來像是同一條繞圈的線被搬到人的裡面。
Wiktionary, "loopy"
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