The Wildcat Nickname
"... football players had not come down from Evanston; Wildcats would be a name better suited to (Coach) Thistlethwaite's boys ... Stagg's boys, his pride, his 11 that had tied Illinois a week ago, were unable to score for 57 minutes. Once they had the ball on the nine-yard line and had been stopped dead by a Purple wall of wildcats." These lines were written by Wallace Abbey in the Chicago Tribune following the memorable Northwestern-Chicago game in 1924 that heralded a new era in Northwestern football. From that day on, all the Northwestern athletic teams have borne the nickname of "Wildcats."
Following the Chicago contest, which NU lost 3-0 on a last-minute field goal by Bob Curley, Northwestern met the famed "Four Horsemen" of Notre Dame and battled the Fighting Irish to a standstill before bowing 13-6. Northwestern's points were scored on two drop kicks by All-American Ralph "Moon" Baker. After that, there could be no question of the appropriate nature of the new nickname.
Years later, Major General Robert H. Wienecke, captain of Northwestern's 1924 squad, recalled: "We were just an average team which developed a spirit that carried us to superb heights against Chicago and Notre Dame. I feel that the reputation gained by the team in those two final games of the 1924 season launched a momentum that was to lead to the Big Ten championship two years later."
Source: Northwestern University Webpage (link).