These patches were given out at the end of the year by Nova Roller Derby.  The "Hat" patch is a bit of a joke.  It's the MVP award for dual pivot-jammers on the team. They couldn't fit "pivot/jammer", so they thought about "pantie" for the patch but thought that sounded crude.  "Helmet cover" wouldn't fit either, so as a bit of placeholder text they wrote "hat".  From what I hear, they never thought of a suitable word so they kept "hat" for lack of a better idea.  It's become an in joke in the league since then.