The term 'HIS '4' WAS RETIRED' refers to the retirement of four professional hockey players: Mel Ott, Bobby Orr, Gordie Howe, and Wayne Gretzky. Mel Ott was a Hall of Fame outfielder who played for the New York Giants from 1926 to 1947. Bobby Orr is a Hall of Fame defenseman who played for the Boston Bruins from 1966 to 1979. Gordie Howe is a Hall of Fame right winger who played for the Detroit Red Wings from 1946 to 1971. Wayne Gretzky is a Hall of Fame center who played for the Edmonton Oilers from 1979 to 1999. All four players had their numbers retired by their respective teams in recognition of their outstanding careers.