quick fact of the day:

According to numerous web sites, such as Professional Jeweler Magazine and Normans of Mosman, tennis star Chris Evert was known for her diamond line bracelets. She lost one during the 1987 U.S. Open, and the game had to be temporarily halted while she prowled the court for it. The "tennis bracelet" incident sparked a new name for the item, as well as a huge jewelry trend.

source: Ask.Yahoo

It's not often that a piece of jewelry is named for an accident, but such is the case with tennis bracelets. Tennis bracelets got their unusual name from an incident involving professional tennis player Chris Evert during a match in 1987. Evert had been wearing an expensive bracelet featuring an inline string of individually-set diamonds. When the clasp snapped, she asked the officials to stop the match until the jewelry could be found. Since that day, bracelets featuring an inline array of diamonds have been called tennis bracelets.

source: WiseGeek

now you know why it's called a tennis bracelet. cool, eh?