ANZAC is the acronym formed from the initial letters of the Australian and New Zealand Army Corps. This was the formation in which Australian and New Zealand soldiers in Egypt were grouped before the landings on Gallipoli in April 1915.
General Sir Ian Hamilton (commander of the British forces in the Dardanelles) and General Sir William Birdwood (commander of the Australians and New Zealanders at Gallipoli) have both claimed a hand in the coining of the term 'Anzac'. However, the most likely explanation of its origin is contained in the official history by CEW Bean, who wrote: One day early in 1915 Major CM Wagstaff … of the 'operations' section of Birdwood's staff, walked into the General Staff office and mentioned to the clerks that a convenient word was wanted as a code name for the Corps. The clerks had noticed the big initials on the cases outside their room—A. & N. Z. A. C.; and a rubber stamp for registering correspondence had also been cut with the same initials.
When Wagstaff mentioned the need of a code word, one of the clerks (… Lieutenant A.T. White) suggested: 'How about ANZAC?' Major Wagstaff proposed the word to the general, who approved of it … Australian sergeants GC Little and HV Milligan were responsible for cutting the original stamp and Bean suggested that the first time the word was used was when Sergeant Little asked Sergeant Milligan to throw him the ANZAC stamp.
'Anzac', would become the name of the main area in which the Australians and New Zealanders fought at Gallipoli, as well as the name of the soldiers themselves.