Antonomasia
In rhetoric, antonomasia is a kind of metonymy in which an epithet or phrase takes the place of a proper name, such as "the little corporal" for Napoleon I, or conversely the use of a proper name as an archetypal name, to express a generic idea. A frequent instance of antonomasia in the Late Middle Ages and early Renaissance was the use of the term "the Philosopher" to refer to Aristotle.