It looks like the Textus Receptus might be the origin of the 'Easter' interjection.
It's hard to believe that translators of the day did not know the meaning of Pesach/Pascha since they used 'Passover'
more than 20 times in the NT.
The use of 'Easter' sounds like replacement theologans were at work. I doesn't seem like a simple oversight.
It's a wrong translation that sticks out like a sore thumb.
It makes me wonder how much translation work the KJV translation team did. They should have corrected it.
The 1535 Coverdale Bible (via Textus Receptus) has it as Easter;
Now whan he had taken him, he put him in preson, and delyuered him vnto foure quaternions of soudyers, to kepe him:
and thought after Easter to bringe him forth to the people.
The 1599 Geneva Bible has translated it correctly as Passover;
And when he had caught him, he put him in prison, and delivered him to four quaternions of soldiers to be kept, intending
after the Passover to bring him forth to the people.