Regarding A&M and the 12th man: A&M trademarked the phrase "12th man" in 1990 well after both teams had been using it. They didn't come after Seattle for using it until 2004. If you don't actively protect your trademarks you lose them. A&M had no grounding over Seattle because they didn't actively protect it. Seattle could have easily won any lawsuit that was thrown their way.
Seattle now pays a nominal fee, essentially nothing, but enough that A&M can say they are protecting their trademark.
Edit: and I believe it was actually Iowa in 1912 who started using it first.
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