E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
An unbeliever, one who disbelieves the Mahometan faith. A corruption of the Arabic Kiafir. It has now become so common that it scarcely implies insult, but has about the force of the word Gentile, meaning not a Jew. Byron has a poetical tale so called, but he has not given the giaour a name.