The term is thought to have originated from a cartoon character named Archie, who was portrayed as a very tall man who could reach up to the sky. The name was then applied to anti-aircraft guns and shells.
During World War I, Archie was used to describe both the guns themselves and the shells they fired. The term was also used in a more general sense to refer to any type of anti-aircraft fire, regardless of the type of gun or shell being used.
Archie was a vital part of the British air defence system during the First World War. Anti-aircraft guns were used to protect cities, military bases, and other important targets from enemy aircraft. Archie was also used to support British troops on the ground by providing cover fire against enemy aircraft.
The term Archie is still used today in the context of anti-aircraft warfare. However, it is now more commonly used in a figurative sense to refer to any type of opposition or resistance. For example, someone who is facing a lot of criticism or opposition might say that they are "under a lot of Archie."