One way to hold this word: a short, hard hair standing up. Not soft hair that lies down and moves when you touch it — a stiff one that stays where it is and your hand. Now put thousands of them side by side. That field of upright, scratchy points is where everything in this word comes from. Set them in a wooden handle and you have a brush. Watch them lift along a cat's back and you have the verb. Move the same picture onto a person who has just been insulted, and nothing physically rises, but the tension, the hardness and the warning are all still there. Move it onto a harbour full of masts, and the whole surface looks furred with upright things.
From Middle English bristil, from Old English bristl/byrst, from Proto-Germanic *burstiz, a stiff hair (compare German Borste, a boar's bristle). The stiff hair is the original meaning, not a later picture.
從中古英語 bristil、古英語 bristl／byrst 來，再往上是原始日耳曼語 *burstiz（硬毛），可以比對德語 Borste（公豬的鬃毛）。也就是說，「硬毛」是這個字本來的意思，不是後來才加上的比喻。
Wiktionary etymology supplied in packet (kaikki:3f6f69a190036ae4:604750544)
Three branches
又短又硬的毛
這一組就是核心畫面本身，一個長在身上，一個被人拿去做工具。
noun · B2
A short, stiff hair that feels rough and scratchy when you touch it — the kind that grows on a pig's back, the ones on a man's chin a day after shaving, and the tiny stiff hairs on the stems of some plants.
硬毛、鬍渣
毛豎起來，跟人跟著繃起來
名詞變成動詞：不是講那些毛是什麼，而是講它們做了什麼——立起來。
verb · B2
When an animal's hair bristles, it lifts and stands up stiff along its back or neck because the animal is frightened or angry; hair on a person can bristle in the same way.
毛豎起來
密密地插滿
把核心畫面放大：一根毛換成一根桅杆、一根天線，整片表面看起來還是同一回事。
verb · C1
To be covered with a great many things that stick out, so that they look like stiff hairs standing up — a harbour bristling with masts, a roof bristling with aerials. It is also used of something packed full of a quality or a problem: a report bristling with mistakes.
布滿、豎滿