The threshing floor of Nacon was a place King David passed through when he was bringing the ark of the covenant from Baale-judah (also called Kiriath-jearim) to Jerusalem. When they reached the threshing floor of Nacon, a man named Uzzah reached out and touched the ark to steady it, and God struck him dead (2 Samuel 6:6).
Because of this incident, David renamed this place "Perez-uzzah," which means "the breaking forth upon Uzzah" (2 Samuel 6:8). In another account of this same event, this place is called "Kidon" instead of "Nacon" (1 Chronicles 13:9).