Easton's Bible Dictionary (1897)
Originally a Saxon word (Eostre), denoting a goddess of the Saxons, in honour of whom sacrifices were offered about the time of the Passover. Hence the name came to be given to the festival of the Resurrection of Christ, which occured at the time of the Passover. In the early English versions this word was frequently used as the translation of the Greek pascha (the Passover). When the Authorized Version (1611) was formed, the word “passover” was used in all passages in which this word pascha occurred, except in Act 12:4.
In the Revised Version the proper word, “passover,” is always used.
Smith's Bible Dictionary (1863)
(Acts 12:4) In the earlier English versions Easter has been frequently used as the translation of pascha (passover). In the Authorized Version Passover was substituted in all passages but this; and in the new Revision Passover is used here.
Hastings' Dictionary of the Bible (1898) & Schaff's Bible Dictionary
EAST'ER (originally the festival of the Anglo-Saxon goddess Eostre), a mistranslation for "Passover," the Jewish feast. Acts 12:4. See Feast.