By-name

An epithet (from Greek: ἐπίθετον epitheton, neuter of ἐπίθετος epithetos, "attributed, added") is a byname, or a descriptive term (word or phrase), accompanying or occurring in place of a name and having entered common usage. It can be described as a glorified nickname. It has various shades of meaning when applied to seemingly real or fictitious people, divinities, objects, and binomial nomenclature. It can also be a descriptive title: for example, Alfred the Great, Suleiman the Magnificent or Władysław I the Elbow-high.

In contemporary use, epithet often refers to an abusive, defamatory, or derogatory phrase, such as a racial or animal epithet. This use as a euphemism is criticized by Martin Manser and other prescriptive linguists.

In linguistics, an epithet only can be a metaphor, essentially a reduced or condensed use of apposition. Epithets are sometimes attached to a person's name or appear in place of his or her name, as what might be described as a glorified nickname or sobriquet. An epithet is linked to its noun by long-established usage. Not every adjective is an epithet. An epithet is especially recognizable when its function is largely decorative, such as if "cloud-gathering Zeus" is employed other than in reference to conjuring up a storm. "The epithets are decorative insofar as they are neither essential to the immediate context nor modelled especially for it. Among other things, they are extremely helpful to fill out a half-verse", Walter Burkert has noted.

Some epithets are known by the Latin term epitheton necessarium because they are required to distinguish the bearers, e.g. as an alternative to numbers after a prince's name—such as Richard the Lionheart (Richard I of England), or Charles the Fat alongside Charles the Bald. The same epithet can be used repeatedly joined to different names, e.g. Alexander the Great as well as Constantine the Great.

...
Wikipedia