E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
April was called Ostermonaththe month of the Ost-end wind (wind from the east). Easter is therefore the April feast, which lasted eight days. Our Easter Sunday must be between March 21st and April 25th. It is regulated by the paschal moon, or first full moon between the vernal equinox and fourteen days afterwards. (Teutonic, ostara; Anglo-Saxon, eastre.)
Easter. The Saxon goddess of the east, whose festival was held in the spring.