|Rabbit on a pillar; entrance to St. Michael's chapel|
from St. Mary's, Beverley, Yorkshire c. 1330
This much we are reasonably sure of; Easter is derived from Middle English ester, itself derived from Old English . There's a very clear Proto Indo-European root there; *aus-, "to shine." Derivatives of *-aus included east, Easter, and Aurora, as well as the name of the Greek dawn goddess, Eos.
You will see a fair number of people stating that Easter is derived from teh name of a pagan goddess named Eostre, or Ostara. Despite urgent and repeated assertions from Neo Pagans, Easter is not Celtic, nor is there a fertility goddess represented by the rabbit named Eostre, nor is she a moon goddess; the fact that the word Easter begins with the word east suggests that if anything, a solar influence is more probable.
We don’t have solid evidence for an English deity named Eostre, except for a brief almost off-hand reference by the Venerable Bede (c. 672–735) in his De temporum ratione, a Latin treatise on the calendar from a Christian perspective. In chapter 15 Bede describes the native English names of the month, and cites the worship of the English goddess Hretha, during the month of Hrethmonath (literally, Heretha's month). Bede then describes
a goddess associated with the vernal equinox, and calls her Eostre (Northumbrian dialect of Old English equivalent to Éastre).
We don't have other references to Eostre in earlyEnglish but it seems most likely that like other Indo-European deities whose names descend from *aus-, Aurora, and Eos, Eostre is a dawn goddess, if in fact Bede is even correct in his assertion that the name of the month was also that of a goddess. Note, by the way, that all the references to an *aus- cognate deity are Germanic, Latin, or Greek; none are Celtic.
Now, it is interesting that English, unlike French or a number of other related Indo-European languages, uses Easter for a Christian feast, rather than a name derived from the Hebrew word for Passover; remember, Christ essentially substitutes the Last Supper for Passover, or Pessach. French Pâques is cognate with Hebrew Pessach, for instance.