To explain the etymology of a word as folk etymology(verb)
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Use "folk-etymologize" in a sentence
"If I were the kind of person to speculate without foundation about the origin of idioms in other words, if I felt competent to folk-etymologize with abandon I would say that perhaps it comes from the notion that a big full skirt and big round cheese might have some topological symmetry."
"Alas, the same Teutonic root almost certainly accounts for harbor, thereby putting paid to George Borrow's attempt to folk-etymologize that word to the Welsh/Gaelic aber ` riverine estuary or confluence. '"