Epithet

Religion
In many polytheistic religions, such as those of ancient India and Iran (the most ancient of which go back to a common Indo-Iranian period), Greece and Rome, a deity's epithets generally reflected a particular aspect of that god's essence and role, for which their influence may be obtained for a specific occasion: Apollo Musagetes is "Apollo, [as] leader of the Muses" and therefore patron of the arts and sciences while Phoibos Apollo is the same deity, but as shining sun-god. "Athena protects the city as polias, oversees handicrafts as ergane, joins battle as promachos and grants victory as nike."

Alternatively, the epithet may identify a particular and localized aspect of the god, such as a reference to the mythological place of birth or numinous presence at a specific sanctuary: sacrifice might be offered on one and the same occasion to Pythian Apollo (Apollo Pythios) and Delphic Apollo (Apollo Delphinios). A localizing epithet refers simply to a particular center of veneration and the cultic tradition there, as the god manifested at a particular festival, for example: Zeus Olympios, Zeus as present at Olympia, or Apollo Karneios, Apollo at the Spartan Carneian festival.

Often the epithet is the result of fusion of the Olympian divinity with an older one: Poseidon Erechtheus, Artemis Orthia, reflect intercultural equations of a divinity with an older one, that is generally considered its pendant; thus most Roman gods and goddesses, especially the Twelve Olympians, had traditional counterparts in Greek, Etruscan, and most other Mediterranean pantheons, such as Jupiter as head of the Olympian Gods with Zeus, but in specific cults, there may be a different equation, based on one specific aspect of the divinity. Thus the Greek word Trismegistos ("thrice grand") was first used as a Greek name for the Egyptian god of science and invention, Thoth, and later as an epitheton for the Greek Hermes and, finally, the fully equated Roman Mercurius Mercury (both were messenger of the gods). Among the Greeks, T. H. Price notes the nurturing power of Kourotrophos might be invoked in sacrifices and recorded in inscription, without specifically identifying Hera or Demeter.

Some epithets were applied to several deities of the same pantheon rather accidentally if they had a common characteristic, or deliberately, emphasizing their blood- or other ties; thus in pagan Rome, several divinities gods, and heroes were given the epitheton Comes as companion of another (usually major) divinity. An epithet can even be meant for collective use, e.g. in Latin pilleati 'the felt hat-wearers' for the brothers Castor and Pollux. Some epithets resist explanation.

Catholics, Eastern Orthodox Christians, and Christians of other churches practice the use of epithets in the veneration of Jesus (e.g., "Christ"; "Prince of Peace"; "The Good Shepherd"), of Mary, Mother of Jesus (e.g. "Mother of God"; "Panagia"), and of the saints (e.g. "Pope Saint John Paul the Great, Saint Theophan the Recluse"). "Our Lady of Lourdes" is essentially periphrasis, except where some aspect of the Virgin is invoked.