The History of College Nicknames, Mascots and School Colors explains the history behind how colleges derived their nicknames, mascots, and school colors. Gary Hudson chose to focus the attention of his book on schools that have Division 1A Football programs, because all the athletic programs at those schools will also compete in Division 1A sports.
Consequently, those schools tend to get more exposure in the media, thereby drawing more attention and curiosity to the college sports fan.