the.com/bristle

means To make the hairs on your skin (or hackles, figuratively) stand up stiffly in anger, indignation, or alarm — or, as a noun, one of those short stiff hairs itself.

from Bristle traces back to Old English 'byrst,' meaning a stiff hair, which is a cousin of similar words across the old Germanic languages — the same root family that gave Old High German its 'burst.' It's also distantly related to the Latin-derived word 'burr,' though the deeper Indo-European root likely just meant something like 'point' or 'sharp projection,' fitting for hairs that stand up stiff and pointed. The emotional sense — bristling with anger — is a natural metaphor: it's literally what hackles do, hairs rising on the back of the neck or along an animal's spine when it feels threatened, a physical display borrowed straight into language for the feeling itself.