A way to hold this word: a swarm you want out of your house. Not one animal with a name, but a mass of small moving things - in the rice, under the floor, in the bed - that eat what is yours and leave dirt and sickness behind. Notice that the picture is not about what the animals are but about what they do to you, and that is why the word can be pointed at a fox, a flea, or a human being.
From the word’s history
Wiktionary traces the word through Old French vermine to Latin vermis, a worm, and notes the related words vermiculate and vermivorous. The oldest picture is therefore a mass of worms, which is exactly the crawling, countless quality the modern word still carries even when it is used of a fox.
字典把這個字經古法文 vermine 追到拉丁文 vermis（蟲），同一條線上還有 vermiculate、vermivorous。最早的畫面就是一堆蟲。今天即使拿來說狐狸，那種「一大群、爬來爬去、數不清」的感覺還在，這正是這個字和 pest 之類的字不同的地方。
Wiktionary, "vermin"
登入就可以看每一支怎麼連回核心畫面。