May the Lord bless you and keep you:b'shem Yah'shua
The Lord make his Face shine upon you:
and be gracious to you:
The Lord lift up His countenance upon you,
and give you peace.
And it's been a memorial of Christ's resurrection first and foremost among Christians since anybody thought to write about it.
We can tell it is early from the controversies that arose over which day to celebrate it: Always on a Sunday, or on a fixed day of the Roman Calender, or on the 14th of Nissan, whenever that would fall. A summary of the early controversies:
The first was mainly concerned with the lawfulness of celebrating Easter on a weekday. We read in Eusebius (Hist. Eccl., V, xxiii): "A question of no small importance arose at that time [i.e. the time of Pope Victor, about A.D. 190]. The dioceses of all Asia, as from an older tradition, held that the fourteenth day of the moon, on which day the Jews were commanded to sacrifice the lamb, should always be observed as the feast of the life-giving pasch [epi tes tou soteriou Pascha heortes], contending that the fast ought to end on that day, whatever day of the week it might happen to be. However it was not the custom of the churches in the rest of the world to end it at this point, as they observed the practice, which from Apostolic tradition has prevailed to the present time, of terminating the fast on no other day than on that of the Resurrection of our Saviour. Synods and assemblies of bishops were held on this account, and all with one consent through mutual correspondence drew up an ecclesiastical decree that the mystery of the Resurrection of the Lord should be celebrated on no other day but the Sunday and that we should observe the close of the paschal fast on that day only." These words of the Father of Church History, followed by some extracts which he makes from the controversial letters of the time, tell us almost all that we know concerning the paschal controversy in its first stage. A letter of St. Irenæus is among the extracts just referred to, and this shows that the diversity of practice regarding Easter had existed at least from the time of Pope Sixtus (c. 120). Further, Irenaeus states that St. Polycarp, who like the other Asiatics, kept Easter on the fourteenth day of the moon, whatever day of the week that might be, following therein the tradition which he claimed to have derived from St. John the Apostle, came to Rome c. 150 about this very question, but could not be persuaded by Pope Anicetus to relinquish his Quartodeciman observance. Nevertheless he was not debarred from communion with the Roman Church, and St. Irenæus, while condemning the Quartodeciman practice, nevertheless reproaches Pope Victor (c. 189-99) with having excommunicated the Asiatics too precipitately and with not having followed the moderation of his predecessors. The question thus debated was therefore primarily whether Easter was to be kept on a Sunday, or whether Christians should observe the Holy Day of the Jews, the fourteenth of Nisan, which might occur on any day of the week. Those who kept Easter with the Jews were called Quartodecimans or terountes (observants); but even in the time of Pope Victor this usage hardly extended beyond the churches of Asia Minor. After the pope's strong measures the Quartodecimans seem to have gradually dwindled away. Origen in the "Philosophumena" (VIII, xviii) seems to regard them as a mere handful of wrong-headed nonconformists.
http://www.newadvent.org/cathen/05228a.htm
You can't tell me that St. Polycarp, who was raised Christan and knew St. John was busy celebrating a pagan holiday as the resurrection of Jesus.
And as you note, all arguments based on the English word for the holiday are a red herring, since the word in nearly every other language comes from Pesach. Can't help it if the English had to be non-conformist here, but Polycarp, Iraneus, and such didn't speak English, and didn't call it Easter. For them and those who followed, the holiday was first and foremost the anniversary of the resurrection of Jesus.
The fact of all these controversies is further proof of how important it was to these church leaders. All the spring symbols that would cluster around the holiday fail in comparison to what always was foremost and most central to Easter: Jesus' death and glorious resurrection. Unlike Christmas, which is a commemoration, Easter has always been an anniversary, one which heralds the dawning of our salvation. Alleluia!