ANTONOMASIA

a figure of speech in which some defining word or phrase is substituted for a person's proper name (for example, the Bard of Avon for William Shakespeare). In fiction, the practice of giving to a character a proper name that defines or suggests a leading quality of that character (such as Squire Allworthy, Doctor Sawbones) is also called antonomasia. The word is from the Greek antonomasa, a derivative of antonomzein, to call by a new name.