“Why are wedding showers and baby showers called ‘showers’?”
It’s a good question. We couldn’t find a definitive answer in either R. Brasch’s “How Did It Begin?” or William S. Walsh’s “Curiosities of Popular Customs.” However, we’ve always heard the explanation that showers are so-called because the guest-of-honor is “showered” with gifts. Several websites second the theory, including BrideAndGroom.com. (It also gives the legend for the origin of the bridal shower: when a bride’s father withheld her dowry because he didn’t approve of her husband-to-be, her friends stepped in to provide her with everything she needed to start her new home.)
The shower of gifts may also have been a literal one -- Beth Montemurro’s “Something Old, Something Bold” mentions the Victorian bridal shower custom of placing small gifts inside a parasol, which would rain down on the bride-to-be-when opened.
Baby showers seem to have taken their name from bridal showers. While celebrating the birth of a baby is a long-held tradition in many cultures, referring to it as a shower seems to be relatively recent.