Like St. Nicholas' name morphing into Santa Claus, so too has the Easter Hare evolved into the Easter Rabbit and Easter Bunny. In a previous article entitled The Origins of the Easter Rabbit I discussed how the word Easter itself and the tradition behind a hare or rabbit delivering eggs at Easter came from customs associated the old Saxon Vernal (Spring) Equinox festivals which survived and merged into our present day Easter customs when the Saxons converted to Christianity. Like many of our Christian holiday customs, the Easter Rabbit has its roots in pre-Christian customs which survived the abandoning of the old religion and embracing of the new Christian religion. At Easter this is especially true of customs involving the celebration of rebirth and renewal, which were associated in pagan times with new life of spring, as Easter is the Christian celebration of Christ's resurrection and new life for mankind.
Originally the rabbit associated with Easter was a hare which is a close cousin to the rabbit and is found in both Europe (where it is more common) and the United States (the jack rabbit of the Southwest is a hare and not a rabbit). The main difference between a rabbit and a hare is that hares tend to be larger, nest in shallow indentations above ground rather than in underground burrows and, finally, hares give birth to young which have fur and whose eyes are open at birth as opposed to rabbits who give birth to young who are initially hairless and whose eyes do not open until a few days after birth.
In The Origins of the Easter Rabbit article I discuss how the tradition of the Easter Rabbit evolved and made its way from Germany to the rest of Europe and then to North America and beyond.
While it is easy to explain how the Easter Hare became the Easter Rabbit given that the two are practically identical as far as looks are concerned and the fact that rabbits are more common in the U.S. But, the question of how did hares and rabbits come to be known as bunnies is a more difficult question. In fact, in my research, the best I could do is find a consensus, of sorts, of guesses.
The consensus of guesses that I found was that our word bunny comes from the Scots Gaelic word bun which was used to describe a swelling, a stump or a root. The term bun appears to have made its way into English where, in the sixteenth or seventeenth century, it was used to describe swellings, human rear ends, and the small tail of rabbits. The word was also applied to small, individual loaves of bread which came to be known as buns (more commonly dinner rolls in the U.S.). As near as most can determine, the term bun was applied in English first to the tail of the rabbit, then its entire rear end. Ironically, the word was also originally applied to the tail of a squirrel. Somewhere along the line the diminutive bunny appeared, first as a term of endearment to describe a child or woman and then later it began to be used to describe young rabbits and squirrel's. In time the term was dropped from squirrels but stuck with rabbits, especially young rabbits. It also tended to fall out of use as a term of endearment for women and children.
Regardless of its origin, the term bunny is now used almost interchangeably with rabbit. However, while synonymous with rabbit, the term bunny still conjures up a softer, cuter image in most people's minds and this can be seen more vividly when comparing images of the Easter Rabbit from a century ago with more recent images of today's lovable Easter Bunny.