Please state in which country your phrase tends to be used, what the phrase is, and what it should be.
Example:
In America, recently came across "back-petal", instead of back-pedal.
Also, still hearing "for all intensive purposes" instead of "for all intents and purposes".
obviously comes from a mishearing by someone who didn't read books
This is assumptive and prescriptive. The link I sent demonstrates that it's been used extensively and for a long time by people who not only read books, but write books. I'm on board that "set foot" is the better phrase and likely to be the earlier one, but trying to dictate which is correct is - respectfully - a fool's errand.
