Think of a liquid that is cold in the bottle and still burns a hole in your sleeve. Nothing is hot; the stuff simply eats through whatever it touches, and the mark it leaves does not wash out. That is what caustic names. The word then does the same job on words: a caustic line is short, cold and leaves a mark on the person it lands on.
From the word’s history
Wiktionary traces caustic to Latin causticus, from Ancient Greek kaustikos (burning), from kaustos (burnt). Burning is in the word from the start.
Wiktionary 記錄 caustic 來自拉丁文 causticus，再往前是希臘文 καυστικός（會燒灼的），源自 καυστός（被燒過的）。也就是說，「燒」這件事從一開始就寫在這個字裡。化學的用法離字根最近，講話那個用法則是把同樣的畫面借過去用。
Wiktionary entry 'caustic' (kaikki:3f6f69a190036ae4:676606977), etymology_text: 'From the Latin causticus (burning), from Ancient Greek καυστικός (kaustikós, burning), from καυστός (kaustós, burnt) + -ικός.'
登入就可以看每一支怎麼連回核心畫面。