caustic

Caustic comes from Latin causticus, meaning "burning," which came from Greek kaustikós, also "burning." That Greek word grew from kaustós, "burnt," plus the adjective-forming suffix -ikós.

The facts here don't trace a shift in meaning — the word has meant "burning" from Greek through Latin into English, whether applied to a chemical or a remark.

Given only the facts above, no specific English cognate can be named — but the root sense of burning is baked into every layer of its history, from Greek to Latin to English.