The etymological fallacy is a genetic fallacy that holds, erroneously, that the present-day meaning of a word or phrase should necessarily be similar to its historical meaning. This is a linguistic misconception. An argument constitutes an etymological fallacy if it makes a claim about the present meaning of a word based exclusively on its etymology. A variant of the etymological fallacy involves looking for the "true" meaning of words by delving into their etymologies, or claiming that a word should be used in a particular way because it has a particular etymology. A similar concept is that of false friends.
An etymological fallacy becomes possible when a word has changed its meaning over time. Such changes can include a shift in scope (narrowing or widening of meanings) or of connotation (amelioration or pejoration). In some cases, meanings can also shift completely, so that the etymological meaning has no evident connection to the current meaning.