How the word Easter was written into the Bible

In the book of Acts Chapter twelve and verse four it says,  And when he had apprehended him, he put him in prison, and delivered him to four quaternions of soldiers to keep him; intending after Easter to bring him forth to the people. 

 Easter is supposed to have been originally the name of a heathen feast, which occurred in the month of April. 

It was afterwards applied to the Jewish feast of the passover, which occurred about the same time. 

Tyndal, in his translation of the Bible into English in 1526, used this word instead of passover, and our English translators in 1611 retained it in their version. But there was no Christian feast called Easter in the days of Peter. 

And the word Pascha which is here translated Easter, means passover, and should have been so translated. Bring him forth; for trial and condemnation  intending after Easter--rather, "after the Passover"; that is, after the whole festival was over. (The word in our King James Version is an ecclesiastical term of later date, and ought not to have been employed here). (JFB)

The Passover Kept by Faith

  Hebrews 11:28 Through faith he kept the passover, and the sprinkling of blood, lest he that destroyed the firstborn should touch them.

(KJV)

 Moses kept the passover.  God told him that he would destroy the first-born of the Egyptians, but would spare all those whose doors were sprinkled with the blood of the paschal lamb. Moses believed this, kept the passover, and sprinkled the blood. 

(Exodus 12:21)

Exodus 12:7 And they shall take of the blood, and strike it on the two side posts and on the upper door post of the houses, wherein they shall eat it.

Exodus 12:13 And the blood shall be to you for a token upon the houses where ye are: and when I see the blood, I will pass over you, and the plague shall not be upon you to destroy you, when I smite the land of Egypt

Exodus 12:23 For the LORD will pass through to smite the Egyptians; and when he seeth the blood upon the lintel, and on the two side posts, the LORD will pass over the door, and will not suffer the destroyer to come in unto your houses to smite you.

1Peter 1:2 Elect according to the foreknowledge of God the Father, through sanctification of the Spirit, unto obedience and sprinkling of the blood of Jesus Christ: Grace unto you, and peace, be multiplied.

Through faith ( in God’s promise, that upon seeing the blood of the paschal lamb upon the upper doorposts, and the two side-posts of the houses of the Israelites, he would pass over them, when he slew the first-born of the Egyptians, Ex 12:13,23) he kept the passover, and (observed) the sprinkling of (the) blood (of it; and this he did), lest he that destroyed the firstborn (see note on 1Co 10.10) should touch them (PLWL)

Through faith he kept the passover (Ex 12:3-30). He kept it because God commanded and he believed all God promised. 

   The sprinkling of blood. The blood of the lamb sprinkled on the door posts. He not only believed that this would protect Israel's first born, but his faith went beyond the type to the Lamb of God. (PNT)

The Passover Lamb in Corinthians

What does the Bible tells us about the Passover

 Purge out therefore the old leaven, that ye may be a new lump, as ye are unleavened. For even Christ our passover is sacrificed for us: 

  (I Corinthians 5:7)