Fourth month of the Old English calendar
For an overview of the Old English calendar and links to the other months, see the summary page.
The fourth month of the year, corresponding approximately to the Roman and modern month of April, was called Eosturmonath. Bede, writing in 725, tells us:
Eosturmonath has a name which is now translated "Paschal month", and which was once called after a goddess of theirs named Eostre, in whose honour 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-honoured name of the old observance.
--Bede, On the Reckoning of Time, Chapter 15. Translated by Faith Wallis.
"Paschal" is the Christian festival called Easter in modern English. Evidently someone had been following Pope Gregory's advice to the early Christian missionaries sent to the English! Pope Gregory advised Bishop Mellitus:
The temples of the idols in that nation ought not to be destroyed; but let the idols that are in them be destroyed; let holy water be made and sprinkled in the said temples, let altars be erected, and relics placed. For if those temples are well built, it is requisite that they be converted from the worship of devils to the service of the true God; that the nation, seeing that their temples are not destroyed, may remove error from their hearts, and knowing and adoring the true God, may the more familiarly resort to the places to which they have been accustomed. And because they have been used to slaughter many oxen in the sacrifices to devils, some solemnity must be exchanged for them on this account, as that on the day of the dedication, or the nativities of the holy martyrs, whose relics are there deposited, they may build themselves huts of the boughs of trees, about those churches which have been turned to that use from temples, and celebrate the solemnity with religious feasting, and no more offer beasts to the Devil, but kill cattle to the praise of God in their eating.
--Bede, Ecclesiastical History of the English People, Book I Chapter 30.
So who was Eostre, the goddess who gave her name and her festival to the Christian Easter?
Kathleen Herbert says that 'eostre' in the Germanic languages means 'from the east' and is cognate with the word for 'dawn' in several Indo-European languages including Greek, Latin and Sanskrit (Herbert 1994). The Old English season of summer, when the days are longer than the nights, begins at the spring equinox, and Eostre's month would be the first month of summer. This would be consistent with Eostre as a goddess of the dawn and the coming of the sun, an altogether kinder and gentler image than the goddess of the previous month, Hretha.
If Eostre's festival was also associated with the return of life in the spring, this may have helped her feast merge with the Christian festival of Easter, which celebrates the return of Christ to life. It may not have been at all difficult for people to carry on celebrating the return of sun, light, warmth and life, with a different name attached to the associated deity.
Full-text sources available online are linked in the text.
Bede: The Reckoning of Time. Translated by Faith Wallis. Liverpool University Press, 1999, ISBN 0-85323-693-3.
Herbert, Kathleen. Looking for the Lost Gods of England. Anglo-Saxon Books, 1994. ISBN 1-898281-04-1.