As Margaret Brown says, Bede attributed the Easter festival to Eostre and as far as the name is concerned she was correct. However, both the spring and autumn equinoxes, like the solstices, have been seen as times for celebration since the days of the early humans.
The Greek pagans, certainly from the time of Pythagoras, some 700 years before Jesus, celebrated the death and resurrection of their god-man in their passion plays, performed at the spring equinox, just as they celebrated his miraculous birth from a virgin at the winter solstice.
Pythagoras, who was a great teacher of religion, although he is mainly thought of today as a mathematician, coined the term philosopher, seeker of knowledge, for himself and his mathematical studies were part of the search for knowledge, especially concerning the earth and mankind. Both he and the philosophers who followed him, as well as many early Christians, saw the death and resurrection in the mystery plays as allegories. It was only the ‘uninitiated’ who believed in a literal, historical happening.
Modern philosophers would find the Sunday Times newspaper’s best seller The Jesus Mysteries very enlightening.