Air Defence Artillery was earlier called the ‘Anti Aircraft Artillery’, generally referred to simply ‘anti-aircraft’ and abbreviated as AA, a term that remained in general use into the 1950s.
Nicknames for anti-aircraft guns include AA, AAA or triple-A, an abbreviation of anti-aircraft artillery. ‘Ack-ack’ (from the spelling alphabet used by the British for voice transmission of “AA”) and Archie (a World War I British term probably coined by Amyas Borton and believed to derive via the Royal Flying Corps from the music-hall comedian George Robey’s line “Archibald, certainly not!”) were the other commonly used terms, especially by the British.
Air Defence was first used in 1925 when Great Britain formed the Air Defence of Great Britain Command. Nowadays, AA is hardly used with the term Air Defence being the established norm.