I have one of these tee shirts that I workout in and wear cycling. I bought it because when I was at Clemson back in the day 1968 to 1972 the people from up north would call southerners "Grits" because we loved grits and they did not we did not mind at all. We called them "Yanks" they did not mind either because it was a friendly rivalry at least that's the way it was in my particular dorm. So we were known as "Clemson Grits". That is the meaning for me with this shirt and the reason I bought it.
senior season when his singular determination and competitive fire helped us close out games that we had otherwise often lost, eventually leading us to the Sweet 16. It was co-opted from there and somehow applied to the whole program as a rallying moniker since.