Pesach (Passover) vs. Easter...
In the early church, immediately after Christ's earthly ministry, the church regularly observed the Passover as the memorial when Christ was slain, and then the “Lord's Day” as the celebration of his resurrection. Invariably, for at least the first few generations, it was observed on the 14th day of Nisan (after the new moon), which was based on the biblical, lunar calendar, identical to that which was followed in Judaism. We know that in the second century, there was a habit of some Christians to observe the resurrection on a Sunday, regardless of what day of the week the Passover fell upon. Because there were some that rigidly observed the Resurrection on the third day after the Passover on the 14th of Nisan, and others observed the Resurrection on the Sunday of that week, the entire week was kept as a holiday by Christians, known as the “Pasch” or “Passover” week.
It is noteworthy that there was no one in the church who had ever heard of an “Easter” celebration for Christians. There was no such thing as “Ash Wednesday” or “Lent”. These were completely foreign to anything having to do with Christianity.
Throughout the 2nd and 3rd centuries, the church kept the Pasch week in chronological harmony with Judaism, since Christ was the “Passover Lamb” in the Christian understanding. This was despite the growing anti-Semitism in many areas of Christianity.
Periodically, there was some effort to “standardize” the day that would recognized as the day of Resurrection. The debate would normally be between churches in the West, following the Latin Rite, versus the Asiatic or Greek churches, and it was question of whether to reckon the resurrection as two, or three days after the 14th of Nisan, or always observe the resurrection on the first Sunday after the 14th. The debate was chronicled by a number of early church historians, such as Eusebius. Following is the account of how Victor, Bishop of Rome, in the late 2nd Century, tried to convince Polycrates, Bishop of Ephesus, to go along with the Western recognition of the Resurrection on Sunday :
Irenaeus intervened, and argued that it shouldn't be a divisive point. The conclusion of such dialogue was that both East and West churches were observing their respective traditions that they were handed down from the apostles before them, and kept communion with one another, regardless of the exact day they observed during the Pasch week.
A new challenge arose, however in the 4th Century. Despite the fact, as documented by many of the early church fathers and ecclesiastical writers, that the apostolic churches were right in observing the Pasch, starting on the 14th of Nisan, coinciding with the Jewish Pasch, Constantine, the Emperor of Rome, had a different idea. He wanted to make the observation of the Paschal week uniform for Christians throughout the empire. Constantine targeted those who followed the biblical calendar because, in his opinion, it meant the church was too dependent on the Jews, whom he considered “Christ killers”. As recorded by Eusebius, Constantine declared at the Council of Nicea:
Besides declaring that Sunday would be the one and only day that Christ's resurrection would be celebrated, he made one other very important, and very significant change to when it would be celebrated.
The addition of the idea that resurrection had to be celebrated on a Sunday after the spring equinox was a decisive break with the biblical calendar for the Passover. Consequently, this is why we have years where the Christian observation of the passion of Christ is up to a month off from the Jewish Passover that Christ participated in at the time of his death! On those years, the 14th of Nisan falls before the Equinox, so Jews observe the passover then, but Constantine's decree bound many Christians from recognizing it as a Christian holiday.
However, Constantine's arbitrary addition of the idea of Spring Equinox had one other even more damaging effect.
In the Celtic and Germanic areas where the Roman Empire had spread, there was already a popular spring holiday that took place 14 days after the new moon subsequent to the equinox. That was the spring fertility festival of Oester.
Oester, or “Ostara” in some cases, as a fertility rite, utilized imagery of hares (ie. Bunny rabbits!) because of their known promiscuity and fertility. Another tradition associated with Oester is the distribution of colored eggs, which were symbolic of an ancient creation-rebirth mythos that extends back to Babylon, where Oester was otherwise known as Ishtar.
It is widely believed that the etymology of the very word “Easter” comes from the spring fertility goddess Oester, whose festival is 14 days after the new moon, after the Spring Equinox.
Over the course of time, since the new holiday was detached from the Jewish Pesach from which it was conceived, and reattached to the pagan spring festival, the very word “Paschal” in Christian terminology was supplanted by the name of the pagan festival, “Easter”. It was considered so synonymous that even the King James Version translators, in Acts 12:4, when faced with the Greek word “pascha” translated everywhere else as “Passover” actually translate it was “Easter”.
Thus, we can see the very deliberate and obvious hijacking of what was the meaningful memorial of Christ, the (Jewish) Passover lamb, by paganism, leaving the institutionalized church with a counterfeit holiday, replete with all the symbolism that it garnered all the way back to the earliest days of heathenism. Just calling it “Easter” is declaration of how complete Constantine's assault on the truth was.
In answer to the three questions posed initially, (why don't passover and Easter coincide, the use of the very word “Easter”, and the symbols of rabbits and eggs), the answer is simply found in the history of the 4th century church. Constantine, because of his anti-Semetism, ordered that the Christian holiday be changed from coinciding with it's Jewish origins, and take place on or about the time of a popular pagan holiday, which eventually eclipsed much of the imagery and meaning of the Christian holiday.
So the only remaining question would be, do we, as Christians, continue
to observe the pagan-rooted festival of Oester, or do we, as a community,
seek to worship Christ, who, as our “passover, was sacrificed for us”
(1 Cor 5:7)? There is no justifiable reason, in my estimation, that
the church should hold to the arbitrary date that Constantine picked,
over the biblical celebration that actually has meaning, and was actually
observed by the apostles.