It appears that the word "Easter" is derived from the name of an old Anglo-Saxon fertility goddess associated with the east who had a springtime festival. The German word is "Ostern," and since the Anglo-Saxons were originally a Germanic tribe, it's pretty clear that the words are related. While old habits apparently die hard in the English and German languages, it's pretty clear that most traditionally Christian nations name the Pasch as the proper name of the feast of Christ's resurrection. 

The Reckoning of the Pasch

In the early days of the church, Christians kept the Pasch in the same manner as the Jews, beginning on the 14th of Nisan. But as time went by, Christianity developed distinctive observances that differed from Jewish practices. 

In the church at Rome, it became customary to celebrate the Pasch on the Sunday following 14 Nisan, in order to commemorate Jesus' rising on the first day of the week. This became a controversy in the late Second Century. Victor I, the bishop of Rome, argued that the churches of Asia Minor should follow the Roman practice, rather than celebrate the Passover on 14 Nisan in the Jewish manner. 

Since the early centuries, the Christian churches used the official Julian civil calendar of Rome to calculate the date of the Pasch. Since it was not always easy to know the date of the Equinox, calendar tables were prepared years in advance. The Roman method of calculating is explained here by the English scholar, the Venerable Bede, who wrote a definitive work on the subject around 700 A.D.: "The beginning of this month ought to be observed according to this rule, so that the 14th Moon of Easter never precedes the vernal equinox, but correctly appears either on the equinox itself (that is March 21) or after it has passed." 

In the early centuries, during persecution by the Roman Empire, Christianity was a loose collection of local churches each led by an independent bishop. Since there was no central authority, not every local church agreed with the Roman method. For centuries, the various churches squabbled about the correct time for celebrating the Pasch. 

A concord was finally established at the Council of Nicaea in 325 A.D. The Council of Nicaea is best known for establishing and affirming the doctrine of the Trinity. Other proclamations were made, including the method of calculating the date of Easter. The synodical letter of the Nicene council reported, "We further proclaim to you the good news of the agreement concerning the holy Easter.... all our brethren in the east who formerly followed the custom of the Jews are henceforth to celebrate the said most sacred feast of Easter at the same time as the Romans...." 

The council emphasized that Easter should never occur during the Passover, due to antagonisms toward the Jewish people and some apparent inconsistencies in the Jewish calendar.

In this way, the Council of Nicaea established a common celebration of the Pasch. In the centuries following Nicaea, the church became increasingly uniform in other doctrines and practices, and centralized in authority. Nevertheless, the issue of Easter had come up again and again throughout church history, and there remain differences to this day.