Ah, thanks. Then I misremembered my high school chemistry from 25y ago. I thought rust (the verb) is oxidation and that when you add an acid, it would be reduction (to get back the iron).

Acid / base and oxidize / reduce are mostly orthogonal. Acid / base is about moving around protons while oxidize / reduce is about moving electrons.

There's a table here: https://www.vedantu.com/question-answer/acid-base-reactions-...

"Acid" is from Latin acidus (sour, sharp, tart) by way of French.

"Oxygen" is a word invented in 1777 by Antoine Lavoisier, from the Greek oxys (sharp, acid): same thing!

Lavoisier also invented "oxide" from ox(ygène) + (ac)ide.