The Cornish are a Celtic people originating from Cornwall in the far south west of the British isles. They have their own lesser used language, a member of the Brythonic group of Celtic languages that also includes Welsh and Breton. The language declined after the middle ages with only a handful of speakers by the 19th century. Luckily the language has experienced a revival over the last century and now there are several thousand speakers.
Cornwall and the Cornish have long been associated with mining and mineral extraction, the ancient Greek geographers tell how the Cornish were very civilised due to their interactions with Mediterranean merchants seeking metals. Cornwall is blessed with an abundance of minerals of all types, too many to discuss here, but the most important being Tin, Copper, and more recently China Clay (Kaolin).
The Cornish as a people have suffered any trials and tribulations over the centuries. They were constantly at war with the ever encroaching Anglo-Saxons. By the middle ages they were governed by a powerful Duchy given to the eldest son of the English monarch, with their own parliamentary and legal system. There was a flourishing of literature centred around Cornwall, Tristan & Iseult, King Arthur, etc.
In the mid sixteenth century however things changed, Henry VIII changed the state religion and Cornwall was forced to change with it. During the reign of his son Edward the Cornish language was removed from church services and English forced in its place. As a result a bloody war was fought by the Cornish against the English which claimed the lives of upwards of 10 percent of the Cornish populace.
During the 17th century Wars of the Five Peoples (Commonly known as the English Civil War) the Cornish sided with their Duke and his father King Charles I against the English parliament (like the Scots and Irish, the Cornish still had their own parliament at this point and were fearful that they would lose it should the English parliament win). Although the Cornish Army(as it called itself) was one of the most successful armies in the war, conquering a large swathe of southern England. However the war did not go so well elsewhere and so the Cornish leader suggested that the Duchy should seek a separate peace with the English, governing themselves. The King did not take kindly to this and had the leader, Richard Grenville, arrested. With the eventual defeat of the royalists, Cornish institutions were dismantled. The restoration of the throne saw a resurgence in the Duchy, the parliament and the courts, but by the 1750's the parliament had become politically dangerous, calling for sovereign powers, and was suppressed.
During the 18th and 19th centuries the Cornish continued a long-standing seafaring tradition, supplying many officers to the new colonies in Australia, Bligh and King amongst them. Lieutenant Zachary Hicks was Cook's second in command, he was not only the first of the expedition to set eyes on the Australian continent, at Botany Bay he was the first of the party to set foot on Australian soil. Not many of the convicts sent to Australia were Cornish, though on the First Fleet were James Ruse(Australia's first farmer) and Mary Bryant (With her husband William), all of whom were Cornish.
The first large scale emigrations from Cornwall to Australia were nonconformists going to South Australia for more religious freedoms. As soon as minerals like copper were discovered they sent back home for friends and relatives, the proverbial Cousins Jack, thus starting the flood of Cornish people into Australia from the 1830s and 40s onwards. In the 1840's there was potato famine in Cornwall, but, due to the fact that the Cornish were already well prepared to emigrate, there was little loss of life.
The Australian gold-rushes were like a magnet to the Cornish, not just from Cornwall and other areas of Australia, but from the USA, Mexico, Brazil, Canada, Peru etc. (The World's two largest gold nuggets were discovered by Cornish diggers). Later many Cornish miners leaving southern Africa would come to Australia as well.