Much has been made in recent years of the 12th man—the importance of their influence, their perseverance, their loyalty. But even a casual football fan knows that there are only 11 players per side on the field. Who is this 12th man?
“The last one is that we want to win the twelfth man. We want to have a great Warrior spirit,” Terwilliger said, “That’s East Stroudsburg football. That’s our process, and that’s how we are going to approach things.”
— Ronald Hanaki, The Stroud Courier, 19 Sept. 2019
The 12th man is the fan, and in the NFL, the phrase is now most commonly associated with the Seattle Seahawks, who now generally refer to their fanbase as the 12s (a gender-neutral version of the 12th man). The fan support has had a huge impact on opponents who play the Seahawks at home. In 2005, fans notoriously rattled the New York Giants enough that they committed a whopping 11 false-start penalties and missed three field goals for a loss. In 2013, fans at Seattle's CenturyLink Field broke records during a game against the New Orleans Saints, where the crowd noise registered 137.6 decibels—only 2.4 decibels quieter than an aircraft carrier's deck, and only 12.4 decibels short of eardrum rupture.
But the phrase predates the Seahawks by 76 years: it was first used in Minnesota Magazine in 1900 in an editorial about college ball: "The mysterious influence of the twelfth man on the team, the rooter, should be as great as any of the rest." As football increased in popularity, so did the phrase 12th man.
The phrase is historically associated with Texas A&M. The 12th man is a long-standing Aggie tradition: Aggie fans have taken up 12th man in honor of E. King Gill, a squad player for A&M who was called down from the press box during the 1922 Dixie Bowl and stood on the sidelines, ready to help the injury-ridden Aggies should he be called upon. Gill's support and encouragement became the stuff of legend. It helped that 12th man was already known to A&M fans: it showed up in a 1921 article in the A&M The Battalion that talks of the psychological impact of "the old yelling army[...] the twelfth man."
Texas A&M actually holds the trademark to the 12th man in reference to fans, which led to a legal scrape between A&M and the Seahawks. In 2006, the suit was settled out of court; the Seahawks could continue to use the phrase of its fans, but only under license from A&M.