In The Reckoning of Time (written in the year 725 by a monk named Bede) we learn of the goddess Eostre, whose name became Easter.
In olden time the English people calculated their months according to the course of the moon. Hence, after the manner of the Greeks and the Romans, the months take their name from the Moon, for the Moon is called mona and the month monath.
The first month, which the Latins call January, is Giuli; February is called Solmonath; March Hrethmonath; April, Eosturmonath; May, Thrimilchi; June, Litha; July, also Litha; August, Weodmonath; September, Halegmonath; October, Winterfilleth; November, Blodmonath; December, Giuli, the same name by which January is called.
Hrethmonath is named for their goddess Hretha, to whom they sacrificed at this time. Eosturmonath has a name which is now translated “Paschal month”, and which was once called after a goddess of theirs named Eostre, in whose honor feasts were celebrated in that month. Now they designate that Paschal season by her name, calling the joys of the new rite by the time-honored name of the old observance.
(see also: Mysteries of Easter and the Tree of Life)