Not booing. Just cheering.

Why do sports fans almost exclusively call out players names in unison when the name can be made to sound more like a boo then a cheer?

I can't tell you how many times I have had to explain to an inexperienced sports fan that the crowd is not booing but simply calling the name of a player that sounds like a boo. 

For the Green Bay Packers, it's running back John Kuhn.

"Kuhn!" Packers fans shout whenever he touches the the ball. 

Aaron Rodgers is their superstar quarterback and Clay Matthews is their defensive juggernaut, but the fans never call out "Rogers!" or "Clay!" in unison during a game.    

Just "Kuhn!"  Their effective-but-nothing-special tail back.

For the Celtics of the 1980's it was Robert Parish, whose nickname was Chief.  Somehow, Celtics fans managed to transform the vowels in the the word Chief into a low, resonate O sound.

"Chief!" they would call out every time he scored. 

Never a unified cheer for fellow Hall of Famers Larry Bird or Kevin McHale.  

Just "Chief!"

For the current iteration of the Boston Red Sox, it's "Yoook!", the cheer for their first baseman, Kevin Youkilis.

For the New York Yankees  and Dallas Cowboys of ten years ago, it was "Moose!", called out for now retired starting pitcher Kevin Mussina and current NFL analyst and retired fullback Daryl "Moose" Johnson.

What gives?