The word Easter you are referring to appears only once in the King James Bible.It is found in the book of Acts where its references Herod the Great killing James and seeking the life of Peter as well.
And he killed James the brother of John with the sword. And because he saw it pleased the Jews, he proceeded further to take Peter also . . . intending after EASTER (Greek pascha) to bring him forth to the people (Acts 12:2 - 4, KJV).
Taken literally, the above verse suggests that the Easter holiday was at least known, if not celebrated, in the New Testament church. This assumption is, however, not correct. The first century church did not keep Easter, which is a Sunday-based holiday that celebrates a pagan goddess of fertility. They kept the Christian Passover that yearly commemorates the death of Jesus.
Confusion
The confusion concerning this word occurred because scholars, whose orientation was toward Catholic and Anglican Church doctrines, wrote the King James Version Bible. Their bias caused some errors in translating the original Bible text into English. One such error was rendering the Greek word pascha (Strong's Concordance #G3957) incorrectly.
The scholars commissioned to produce an English translation of the Scriptures were all members of the Church of England. The Church, though it split with the Catholics, retained many of its teachings. This included keeping a type of Easter celebration on a Sunday. The translators succumbed to their own biases and pressure from King James (the official head of the church) to create a Bible that agreed with already accepted doctrines. One of the foundational doctrines they were pressured to maintain was the celebration of Christ's death on Easter.
The New International Version Bible correctly translates the Greek word pascha as Passover and not as Easter. It renders Acts 12:4 as "After arresting him, he put him in prison, handing him over to be guarded by four squads of four soldiers each. Herod intended to bring him out for public trial after the Passover."
The Holman Christian Standard Bible also rejects the translation of pascha as Easter. For the verse in question it states, "After the arrest, he put him in prison . . . intending to bring him out to the people after the Passover."The majority of modern Bible translations (ASV, NKJV, TLB, TEV, Holy Bible Faithful Version, and so on) do not translate pascha as the word Easter. They translate it correctly as Passover.