Why grandslam tennis tournament called is grandslam?
The four major tennis tournaments; the US Open, the Open
Championships(wimbledon), Roland Garros (French Open), and the
Australian Open are known as the Grand Slam of tennis. Hitting a
grand slam in baseball scores four runs and is the greatest
accomplishment a baseball player can achieve during one at bat.
Likewise, winning the Grand Slam of tennis involves winning four
tournaments and is considered the greatest accomplishment in
tennis. Because "tournament which makes up part of the Grand Slam
of tennis" is so long it is usually shortened to "Slam".