What is the meaning of Folk_etymology?

A misunderstanding of the etymology of a word based on an inexpert analysis; an etymology that incorrectly explains the origin of a word based on the inadequate judgement of a common speaker of the language instead of etymological expertise.

A modification of a word or its spelling resulting from a misunderstanding of its etymology, as with island, belfry, and hangnail.

Source: wiktionary.org