The Eve of Epiphany (also called Twelfth Night) is believed to commemorate the first manifestation of Jesus Christ to the Gentiles: that is, the arrival of the three Wise Men in Bethlehem.

Christians believe that it was on this day that Christ was revealed to the Three Kings, or the Three Wise Men. The Epiphany, falling on the last of the twelve days of Christmas, is the culmination of the religious Christmas season. The word epiphany may have a primarily secular meaning today, but, as in the case of many words, the meaning of epiphany has changed and adapted itself to different needs over time.

Epiphany, from the Greek epiphaneia, means "appearance" or "manifestation," and was first seen in English around 1310. For three hundred years, its meaning was static: it meant the religious feast day and nothing else. In the 17th century, epiphany began being applied to other manifestations of Christ, such as the Second Coming, and by the mid-1800's it was being used to refer to other divine beings. It was also in the mid-1800s that the meaning of epiphany began to expand beyond the religious. For instance, the essayist Thomas de Quincey wrote of "bright epiphanies of the Grecian intellect."

The process that has carried epiphany from the purely religious into the secular was completed under the powerful influence of 20th century Irish master, James Joyce. In a partial early draft of what would become his novel A Portrait of the Artist as a Young Man, Joyce defined his literary epiphany as "a sudden spiritual manifestation, whether in the vulgarity of speech or of gesture or in a memorable phase of the mind itself."

Joyce used the epiphany in all his fiction, from the short stories of Dubliners to the 600+ pages of Finnegans Wake, a single long epiphany. The narrator in "Araby," a story in the Dubliners collection, is a young boy who realizes suddenly that his own romantic yearnings have made a fool of him. The last lines of the story contain the Joycean epiphany, as the narrator describes "Gazing up into the darkness I saw myself as a creature driven and derided by vanity; and my eyes burned with anguish and anger."

Students of literature have carried the word epiphany into other corners of contemporary life, and today it can carry a range of meanings, including "an intuitive grasp of reality," "an illuminating discovery, realization, or disclosure," or simply "a revealing scene or moment."