Okay What is the origin of annual celebration of pascha? Because I know the celebration of Sunday is apostolic and I know the origins of the word pascha and Easter but I'm interested in learning what is the origin of the festival is
The origins of the celebrations done today are as another poster said, centered on the Passion, Death and ending with the celebration of the Resurrection of Our Lord and Savior Jesus Christ. The debates within the Church are several, some of which the details on have either been obscured or lost to anything but vague (and disputed in meaning) references rather than transcripts of the details (like most Councils have).
But principally the debates centered on when the celebration should occur, when it is was proper to end and perhaps what is part is most important (Passion, Death, Resurrection). Those debates got very convoluted because of the size of the Church, the size of some egos within the Church leadership, ancient modes of communications could take years to establish any unity and language, among probably other things.
In some cases people were using words for a celebration which meant different things to different groups, so they argued over something when it was not even clear either side understood the opposing views position. (sounds like CF sometimes).
What is never true is that the Church invented what they were celebrating or why or the significance of when (which was traditionally centered around the Jewish Passover - logically because in many views of ALL the Gospels that His Passion begins during that annual Jewish events. At first that would be easy to determine the date for Easter, as the Church followed the Jews Passover. Since the Jews did not always agree within themselves on the calendar and kept changing the way it was determined, the Church eventually grew tired of attempting to retain unity of celebration and planning something that varied within the "known" world of the Church.
It was so bad, someone once made a quip of how you could celebrate the joy of Easter in Rome travel weeks to another and people are in morning still over His Death.