The Greek word here translated 'easter' is 'pascha'. Everywhere
else in the KJV the word is translated 'passover'. In modern Greek,
it means either Passover or Easter, depending on the context of the
whole thought.

The name Easter comes from the pagan "goddess" of
antiquity,Ishtar,also variously known as Astarte, Asherah(named in
Scripture), Pallas Athene of the Greeks,and Eostre of the British
Isles, to name a few. All these are related to the worship of the
planet Venus, as is the "Queen of heaven" & the "god of women"
mentioned in Jeremiah.

  The word pascha comes from the Hebrew 'Pesach', which simply means
the Passover.

  The rendering of Easter in Acts 12:4 in the KJV is a deliberate
boo-boo. The Book of Acts was written by Luke, & the observance of
Easter as WE know it DID NOT EXIST in Luke's time. But it WAS known
in 1604,& the AV translators, being almost all Anglicans, observed
it. I think this ONE exception to their rendering of pascha as
Passover was a political ploy to mollify both Anglicans & Catholics.

  However,please don't toss your KJVs because of this! The BASIC
MESSAGE of the verse is unchanged! The KJV remains as one of the
best of all English Bible translations. There's nothing really wrong
w/your KJV! Just bear in mind that it isn't perfect, that no Bible
translation is, & the KJV isn't the only valid English Bible
translation there is. BUT-The KJV & every other valid Bible version
both before & after 1611 came out just as GOD wished! I guess He
allowed such boo-boos as "Easter" to show us the HUMAN side of Bible
translating & to discourage the setting up of any BV as an icon for
eventual worship. I say this because it would've been a simple
matter for God to have preserved the Autographa-the original
writings by the very men to whom God gave His words. But He chose
not to do that. The AUTHOR is always greater than the book,and this
is MUCH MORE SO when the Author is GOD!!