folk etymology 
noun
1A popular but mistaken account of the origin of a word or phrase.Every time I poke around in an area like this, I'm amazed by the range of nascent constructional folk etymologies that are out there....
- So there were lots of these sort of folk etymologies.
- Such folk etymologies are common, but worth verifying.
1.1 [mass noun] The process by which the form of an unfamiliar or foreign word is adapted to a more familiar form through popular usage.Here we see the workings of the process of linguistic change known as folk etymology....
- We've been using eggcorn as a term for the kind of sporadic folk etymology represented by interpreting acorn as ‘egg corn’.
- Smith doubted that Perchta descended from a pagan goddess, but thought that she was the personification of Epiphany (Perchta's Day), derived through folk etymology.