Actually, its not a crescent moon…which would be way too Muslim-y for the people of South Carolina. Its a gorget and supposedly evolved from a flag that was flown by a unit in the Revolutionary War. The unit in question (SC 2nd Regiment under Moultrie) was famous for seizing an island from the British for a few hours before the banner was shot down by British ships and the British ultimately routed the entire regiment. (Vaguely familiar to Fort Sumter…something about SC and losing defenses of islands)
Ironically, the gorget in question was actually a piece more often worn by British officers (Cornwallis sported one, for example.Yeah, the guy who occupied and was the scourge of SC).