Digger is a military slang term for soldiers from Australia and New Zealand. Evidence of its use has been found in those countries as early as the 1850s, but its current usage in a military context did not become prominent until World War I, when Australian and New Zealand troops began using it on the Western Front around 1916–17. Evolving out of its usage during the war, the term has been linked to the concept of the Anzac legend, but within a wider social context, it is linked to the concept of "egalitarian mateship".
Before World War I, the term "digger" was widely used in Australasia to mean a miner, and also referred to a Kauri gum-digger in New Zealand. In Australia and New Zealand, the term "digger" has egalitarian connotations from the Victorian Eureka Stockade Rebellion of 1854, and was closely associated with the principles of "mateship", which may have had resonance from earlier use of the term Diggers as egalitarians. Many Australian and New Zealand soldiers in the Second Boer War, 1899–1902, were former miners, and at the Battle of Elands River (1900), the Australian defenders earned a reputation as diggers, who hastily constructed dugout defences in the hard ground.
Following the landing at Anzac Cove on 25 April 1915 during the Gallipoli Campaign, General Sir Ian Hamilton wrote to General William Birdwood, the commander of the Australian and New Zealand Army Corps (ANZAC), adding in postscript: "You have got through the difficult business, now you have only to dig, dig, dig, until you are safe." However, writer Tim Lycett argues that there is no hard evidence to suggest that Hamilton's message is the reason why "digger" was applied to ANZAC troops in general.