I was watching MNF last night and noticed the guys on the sidelines that hand the footballs to the refs have these big ass smocks with a “K” on them. What does the “K” stand for?
The ordinary game balls are not maintained by the officials before the game. AFAIK, both teams can go through their warm-ups with game balls before the game.
However, the kicker “k” balls (are supposed to) come sealed from the manufacturer, and are kept in the officials’ locker room before the game. This article touches on the purpose of having separate balls for kickers: