:Here's one reference: 
 :A sweeping success or total victory, as in This presentation gave us a grand slam every buyer placed an order. This term originated in the early 1800s in the card game of whist (forerunner of contract bridge), where it refers to the taking of all thirteen tricks. It later was extended to bridge and various sports, where it has different meanings: in baseball, a home run hit with runners on all the bases, resulting in four runs for the team; in tennis, winning all four national championships in a single calendar year; in golf, winning all four major championships. In the 1990s the term was used for four related proposals presented on a ballot at once. 

 :Source: The American Heritage® Dictionary of Idioms by Christine Ammer. 
 :Copyright © 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Company. 

 : To continue the question, what's "The American Heritage® Dictionary" source and can it be considered any more authoritive? There is no official definition of Golf's grand slam, which is why there is no concensus on whether Tiger Woods achieved it.