From university of Miami website:
In 1973, UM’s Athletic Federation, the fund raising arm of the athletic department at the time, commissioned a local public relations expert to develop a distinctive logo. The University had gone several years with a variety of helmet and uniform changes and the Federation noted that a number of major colleges have the initials UM. Miami designer Bill Bodenhamer suggested the "U" idea, which lent itself to slogans like "U gotta believe" and "U is great".

In 2009 the University adopted the split-U logo as the centerpiece of its visual identity system.