Where does the word Easter come from?

Ostara (1884) by Johannes Gehrts
Word Origin
Old English ēastre, after a Germanic goddess Eostre; related to Old High German ōstarūn Easter, Old Norse austr to the east, Old Slavonic ustru like summer.
Perhaps surprisingly, the word Easter is not strictly Biblical - there is no reference to anything similar in the New Testament. Scholars agree that the word was taken from the pre-Christian pagan world - it refers to a festival for a goddess  in the month of April.

English is unusual in this respect. In most languages the word is a derivatiation of the Jewish feast of Passover around which the key events take place (in Spanish 'pascua', for example). There is also more linguistic emphasis on the idea of Holy Week (in Spanish the most common reference point is Semana Santa)

This has lead to some controversy amongst some English-speaking Christians (see here)

An Introductory Dictionary of Theology and Religious Studies