The original lyrics already said "No other gang in college dares to meet us in a muss...".
Somewhere along the line, someone at the U decided to start calling the student section that, saying it stands for Might Utah Student Section, and changed the lyrics to "No rival band of college fans dare meet us in The Muss."
I don't recall hearing "The Muss" until recent decades, but maybe it was before the birth of Utah football in 2004 that they've used it.