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”.
I believe this comes from people trying to show off their education. Traditionally, words with a french descent were pronounced with a silent H. So for example hospital (from French hôpital) is an hospital, where hound (from Germanic hund) is a hound.
This is pretty much deprecated these days and anyone enforcing it is beyond grammar nazi, but it’s interesting to know the pattern.
Source: my secondary school English teacher.