The American Church Dictionary and Cycopedia
A festival in honor of our Lord's Resurrection has been observed from the very foundation of Christianity. This is evident from the early disputes had concerning it, not as to whether such a day should be kept, but as to the particular time when the Festival should be observed. The eastern Christians wished to celebrate the Feast on the third day after the Jewish Passover, on whatever day of the week this fell. The western Christians contended that the Feast of the Resurrection ought always to be observed on a Sunday. This controversy was finally settled by the Council of Nicea, A.D. 325, which decreed that everywhere the great Feast of Easter should be observed upon one and the same day and that a Sunday. In accordance with this decision Easter Day is always the first Sunday after the full moon, which happens upon or next after, the 21st of March; and if the full moon happens upon a Sunday, Easter Day is the Sunday after. By this rule Easter will always fall between the 22d of March, the earliest date, and the 25th of April, the latest day on which it can possibly fall.
The original name of the Festival was Pascha, derived from the Hebrew word for Passover. The more familiar name of Easter is traceable as far back as the time of the Venerable Bede, A.D. 700. The derivation of the word is uncertain. Some think that it is derived from a Saxon term meaning "rising"; others think the word Eost or East refers to the tempestuous character of the weather at that season of the year and find its root in the Anglo-Saxon YST, meaning a storm. Again others derive the word from the old Teutonic urstan, to rise. It is worthy of note that "the idea of sunrise is self-evident in the English name of the Festival on which the Sun of Righteousness arose from the darkness of the grave."
Easter was always accounted the Queen of Festivals the highest of all Holy Days, and celebrated with the greatest solemnity, and the Prayer Book provisions are in keeping with this fact. Churches are decorated with flowers and plants as symbolical of the Resurrection. White hangings for the Altar and White vestments have always been used at Easter in reference to the angel who brought the tidings of the Resurrection, who appeared in "garments white as snow" and "his countenance was as lightning." In the early Church Christians were wont to greet one another on this day with the joyous salutation, "Christ is Risen," to which the response was made, "Christ is risen indeed." This custom is still retained in the Greek Church. This joyous salutation seems to be retained in our services, for instead of the Venite we have as the Invitatory, the Easter anthem, in which we call upon one another to "keep the Feast," for that "Christ our Passover is sacrificed for us," and is also "Risen from the dead; and become the first-fruits of them that slept."
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Miller, William James. Entry for 'Easter Day'. The American Church Dictionary and Cyclopedia. https://www.studylight.org/dictionaries/eng/acd/e/easter-day.html. 1901.