Actually, it started back in the first Ironman, back in Hawaii. Dave Orlowski, one of the original Ironman finishers, a dairy farmer, who provided fine milk to the big cheese plant outside of Madison, was originally a Wisconsin resident. He made the long and arduous journey to Kona to participate in this strange and wonderful race; in fact, it was his first time outside of the great state of Wisconsin. He was awed, and in fact a little overwhelmed, the truth be told, to be so far from home, participating in such an intimidating event, the sounds, smells, and sights of the Big Island so foreign to him, a simple cow farmer from Prarie Farm, WI.
He managed to make it through the swim, but thoughts of pastures, cowchips, and cheese hats soon consumed his mind on the bike. In the middle of the bike leg, he was struggling, feeling uncomfortable, wishing for a familiar face, a friend, something to get him through those next few long miles. The sweat poured down his forehead... all he wished for, was a piece of cheese; something to remind him of home... comfort... alas, there was no cheese to be had in his Bento Box, as the searing heat coming off the lava fields had rendered it to mere Cheez Whiz. And who wants Cheez Whiz at mile 60 on the bike? Not even a Wisconsin dairy farmer. He began entertaining thoughts of quitting...
And then he heard it.
Off in the distance, a familiar ringing. Could it be? The sound got louder as he pedalled on, his stroke becoming stronger, more confident with each "ring" echoing through his ears. There was Sally Gunderson, who had made the trip, unbeknownst to our hero, all the way from Wisconsin, just to ring, ring, ring, that cowbell, and spur Dave onto the finish line.
The rest, of course, is history. The story of Sally and her cowbell and how it rescued Dave from a certain DNF was told and retold, and now, at all levels of triathlon, the course is lined with folks just like Sally ringing, ringing, ringing, that cowbell.
Hope that helps.