Folk etymology (also known as popular etymology, analogical reformation, reanalysis, morphological reanalysis or etymological reinterpretation) is a change in a word or phrase resulting from the replacement of an unfamiliar form by a more familiar one. The form or the meaning of an archaic, foreign, or otherwise unfamiliar word is reinterpreted as resembling more familiar words or morphemes.

The term folk etymology is a loan translation from German Volksetymologie, coined by Ernst Förstemann in 1852. Folk etymology is a productive process in historical linguistics, language change, and social interaction. Reanalysis of a word's history or original form can affect its spelling, pronunciation, or meaning. This is frequently seen in relation to loanwords or words that have become archaic or obsolete.

Examples of words created or changed through folk etymology include the English dialectal form sparrowgrass, originally from Greek ἀσπάραγος ("asparagus") remade by analogy to the more familiar words sparrow and grass. When the alteration of an unfamiliar word is limited to a single person, it is known as an eggcorn.