…is the butchering of common idiomatic phrases. People know more or less how they sound, but not what they mean or how they look. They have probably heard them in passing on a television show or a movie but have never seen them in writing.
It is primarily native speakers who use these phrases incorrectly because non-native speakers do not have the confidence or fluency to attempt idiomatic phrases.
At the moment my pet hates are mute point used instead of moot point, it’s not rocket surgery used instead of it’s not rocket science/brain surgery, and even still used instead of even so.
This is a really interesting article about commonly misused phrases that make one sound unprofessional.