SEC Fan's Guide to Mizzou Baseball: Why "MIZZOU"?

Mizzou is the University’s nickname and is pronounced MIZ-ZOO.

No one is sure who first coined the word Mizzou, but it appeared in the Missouri Alumni Quarterly as early as 1906.

The commonly accepted origin story is that it began as a cheer that has been part of MU athletics longer than anyone remembers:

MIZZOU-RAH! MIZZOU-RAH!  

It's a natural adaptation of the state's name into the commonly used RAH RAH cheers of the later 1800s/early 1900s.

SEC Baseball Fan's Guide
to Mizzou Baseball

It also reflects a common alternate pronunciation of Missouri.  Citizens of the state are somewhat divided between MissourEE and MissourUH as the appropriate way to say the state's name.  This is a long debated and even scholarly pursued question, one which will never be settled to the satisfaction of all.

The VOX Magazine provided a timeline of the origins of Mizzou.

The term Mizzou is incorporated in many Tiger traditions, including cheers and songs (see video below).  A favorite cheer of MU fans is for one side of the stadium/arena/ballpark to shout M-I-Z !!, and the other side replies Z-O-U !!.

Mizzou is actually a registered trademark of the University of Missouri, a branding name used not only by the athletic department, but by the university as a whole, much like Ole Miss.