The general iconography of bunnies and chicks, particularly the Easter Bunny, associated with Easter has roots in paganism and the celebration of spring and fertility. It was later incorporated into the Christian tradition of remembering the day that Jesus Christ rose from the dead, which is also celebrated in spring.
Pre-Christian Germans worshipped many deities, one of whom was Eostre, the goddess of spring and fertility. Her symbol was the rabbit. At the Vernal Equinox, those who worshipped Eostre held feasts in her honor and celebrated the return of spring. Eggs, chicks and bunnies were often associated with rebirth and fertility and were symbols used during the celebrations. As Christianity spread, the church adopted the imagery to make Christianity more appealing to pagans, who they hoped to convert.
The first documentation of the legend of the Easter Bunny dates to the 1500s in Germany. By the 1700s, Germans were immigrating to the Americas and brought the deeply ingrained traditions with them.