The baby showers we know today began during the baby boom era after World War II. The term "shower" came from the practice of "showering" the mother-to-be with gifts and commodities that could get expensive for the parents. This was also the time where the baby shower traditions that are still practiced today originated: the showers were hosted by a close family member or female friend, only women attended, and the mother-to-be opened gifts at the shower in a central, decorated chair.
Since then, baby showers have certainly evolved as far as etiquette. Today it is appropriate to host co-ed baby showers where both men and women can attend and the guest of honor includes the father-to-be as well. Baby Shower Games are also extremely popular, such as the "don't say baby" game and measuring the size of the mother's belly - complete with prizes for the winning guests!
If you're interested in keeping your baby shower traditional, consider sending guests home with elegant baby shower favors which look as classic as the baby shower really is!