From Wikipedia:

In linguistics, an eggcorn is an idiosyncratic substitution of a word or phrase for a word or words that sound similar or identical in the speaker's dialect (sometimes called oronyms). The new phrase introduces a meaning that is different from the original but plausible in the same context, such as "old-timers' disease" for "Alzheimer's disease".

Final thoughts

I recently became aware of the concept from the phrase "toe the line", which people misspell as "tow the line", neither of which I fully understand yet. The more you know.