Salute originated in England. It is said that the British navy used artillery more than 400 years ago. Before a warship enters the port of a friendly country, or meets a ship of a friendly country on the high seas, in order to show no hostility, all the shells in the cannon on board are released, and the coastal gunboat of the other side does the same in return. This practice has gradually become a courtesy to pay tribute to each other. Because the largest warship at that time was equipped with cannon 2 1, firing 2 1 became the highest etiquette.

The number of shots is equivalent to the warship level (the number of guns). 2 1 the highest, and the following times are 19, 17, 15, 13. It is said that even numbers were considered unlucky at that time, so naval guns were all singular, and even numbers are ringing now.

2 1 ringing all the bells is a courtesy enjoyed by the head of state. 1875, the United States officially adopted this etiquette for the president and the national flag for the first time.

2 1 ring, usually sounded by the head of state. Secondly, it sounded 19, which sounded the alarm for the heads of government. Followed by 17, deputy prime minister.