Let me start by saying that the audio in this video isn't the best as it doesn't capture the way that the chant fills the air in the Fieldhouse. Either way, you get a feel for what it is like. When you're in that Fieldhouse everyone in there is family, save for the very, VERY few that go there to root for the visiting team. Memorial Stadium is just as loud but because there are so many more people that fit in there it reverberates more deeply in your chest. Pure awesomeness.

http://www.youtube.com/watch?v=h51be27dN8c

Taken from the KU website:
"KU's world famous Rock Chalk Chant evolved from a cheer that a chemistry professor, E.H.S. Bailey, created for the KU science club in 1886. Bailey's version was "Rah, Rah, Jayhawk, KU" repeated three times. The rahs were later replaced by "Rock Chalk," a transposition of chalk rock, the name for the limestone outcropping found on Mount Oread, site of the Lawrence campus.

The cheer became known worldwide. Teddy Roosevelt pronounced it the greatest college chant he'd ever heard. Legend has it that troops used the chant when fighting in the Philippines in 1899, in the Boxer Rebellion in China, and in World War II. At the Olympic games in 1920, the King of Belgium asked for a typical American college yell. The assembled athletes agreed on KU's Rock Chalk and rendered it for His Majesty."

I hope that explains it Mike! ROCK CHALK!