Folklore suggests that Eostre was a fertility goddess, (oestrogen being a derivative of her name), with eggs and hares comprising symbols of her annual feast day. The latter would go on to be usurped by the cute n' cuddly bunny rabbit, owing to 'unsurpassable demonstrations of seasonal randiness'.
Here's my own collection of Easter symbology - minus said demonstrations - as garnered during last Sunday's parkside trek: