That's a good question and the following links provide some good answers; I prefer the term "Pascha", since Christ is our Passover.
http://www.catholic.com/thisrock/1999/9903chap.asp http://www.turrisfortis.com/easter.html http://home.nyc.rr.com/mysticalrose/pagan8.html In addition to these Catholic resources, in my journey, I have found the small book by Ralph Woodrow (Protestant) -
Easter Is It Pagan? (
Christmas Reconsidered is good, too) to be very helpful in explaining this.
What about the use of
Eastern ("dawn", although some etymologies indicate goddess of the dawn - Aurora, etc) Orthodox/Catholic or
SUNday" (or the days or the week, months, etc.)? Some of the cults - like the Jehovah's witnesses use such tactics (the "Church practices paganism", "devotion to Mary is goddess worship", etc arguments) to try to trip people up and get them to leave the Church.
There are many other resources available; I hope these help a bit!
In Christ's love,
Woody
P.S. Here's a question/answer on this I just found:
http://www.cin.org/users/james/questions/q030.htm