Governor Arthur Phillip had instructions from King George III to
endeavour by every possible means to open an Intercourse with the Natives and to conciliate their affections, enjoining all Our Subjects to live in amity and kindness with them. 
No Aboriginal people ventured into the British settlement at Sydney Cove after February 1788. To comply with his orders, the governor directed that one or more be taken by force. On 31 December 1788, Lieutenant Henry Lidgbird Ball of HMS Supply and Marine Lieutenant George Johnston ambushed two Aboriginal men at Kayeemy (Manly Cove) on the north shore of Port Jackson. A seaman threw a rope around the neck of one man and dragged him into the ship's boat, but the other man escaped. In Watkin Tench's description, his friends attacked the boats as they pulled out, hurling
spears, stones, firebrands, and whatever else presented itself … nor did they retreat … until many musquets were fired over them. 
Captain John Hunter commented:
The terror this poor wretch suffered, can better be conceived than expressed; he believed he was to be immediately murdered. 
The native man, at first called Manly after the place where he was captured, intrigued Tench. 'He appeared to be about thirty years old, not tall, but robustly made', he wrote. At Sydney Cove the captive was taken to the governor's temporary canvas house where his hair was cut and his beard shaved off. After personally scrubbing 'Manly' with soapy water, Tench concluded that he was 'as black as the lighter cast of the African negroes'. He was dressed in a shirt, jacket and a pair of 'trowsers' and an iron handcuff attached to a rope was fastened to his left wrist. This pleased him and he called it Ben-gàd-ee, meaning an ornament, 'but his delight changed to rage and hatred when he discovered its use,' wrote Tench.
The First Fleet officers found that the man's name was Arabanoo. Newton Fowell wrote it as Arooboonoo and Arooboonen, Daniel Southwell as Araboonoo and Henry Waterhouse as Harrabanu. Although he had been captured in the north harbour territory of the Cameragal, Arabanoo's clan is not known. At that time Manly Cove was a centre of Aboriginal resistance where ships' fishing boats were often pelted with rocks.
Acquiring knowledge of their language was a crucial part of Phillip's plan to 'reconcile' Aboriginal people to the occupation of their country and to persuade them to come and live with the colonists. Linguist Jakelin Troy has characterised the capture and 'training' of Arabanoo as 'the first linguistic experiment'. 
Bradley in his journal said Arabanoo soon became
quite familiarised & very happy quite one of the Governors family & had got some of our language as well as communicated much of theirs. 
Phillip's aides obtained a few words from Arabanoo, including gweè-un (fire) and Weè-rong (Sydney Cove).  When shown a 'handsome print' of the Duchess of Cumberland, he cried out 'woman', a name he had just been taught to call the female convicts.  'Much information relating to the customs and manners of his country was also gained from him,' said Tench. For some reason, perhaps the difficulty of acquiring English or 'the unskilfulness of his teachers', Tench thought 'his progress in learning … was not equal to what we expected'. 
Arabanoo relished bread and tea, but rejected strong liquor. When Governor Phillip took him to see HMS Supply, which was leaving for Norfolk Island, he reluctantly stepped on board, but jumped off in terror at the first chance and could not dive under the water because his English clothes kept him afloat. He looked sullen when brought back to the ship but cheered up when Phillip called him to get into the boat to go ashore. 
A quiet and gentle person, Arabanoo was courteous to the colony's women and shared his food with the children. He was disgusted in March 1789 when forced to watch the punishment of runaway convicts who were given 150 lashes each. Tench wrote:
Arabanoo was present at the infliction of the punishment; and was made to comprehend the cause and the necessity of it; but he displayed on this occasion symptoms of disgust and terror only. 
Arabanoo made no attempt to escape when freed from his manacles in April 1789. Captain John Hunter met him on 2 May 1789 when HMS Sirius returned to Sydney with urgently needed food supplies from the Cape of Good Hope. Despite his first experience, wrote Hunter, Arabanoo 'expressed a great desire to come on board my nowee; which is their expression for a boat or other vessel upon the water'. He dined on the ship with Governor Phillip the next day. 
As his ship came into port, Hunter was horrified to see Aboriginal bodies floating in the water or lying unburied on the beaches and caves around Port Jackson. These were the victims of the deadly smallpox epidemic that broke out among the Aboriginal population in April 1789, with the result, according to Bennelong, that 'one half of those who inhabit this part of the country died'.  No white settlers were infected.
Arabanoo helped to bury some of the victims and was present when two children, Nanbarry and Boorong (at first mistakenly called Abaroo) were brought into Sydney suffering from the disease. When Arabanoo was taken by boat to look for his friends, not one living Aboriginal person could be found. Appalled by the sight of decaying bodies, he cried out 'All dead! All dead', then hung his head and was silent. 
The children recovered after treatment by Surgeon John White, but after helping to nurse them through their illness, Arabanoo himself contracted smallpox and died within eight days on 18 May 1789. He was buried in the governor's garden (present Circular Quay precinct) 'to the great regret of every one who had witnessed how little of the savage was found in his manner', wrote David Collins. 
John Hunter, An historical journal of the transactions at Port Jackson and Norfolk Island : with the discoveries which have been made in New South Wales and in the Southern Ocean since the publication of Phillip's voyage, compiled from the official papers, John Stockdale, London, 1793
Watkin Tench, A complete account of the settlement at Port Jackson, in New South Wales, including an accurate description of the colony; of the natives; and of its natural productions, G Nicol and J Sewell, London, 1793
David Collins, An account of the English colony in New South Wales from its first settlement in January 1788, to August 1801, T Cadell and W Davies, London, , 2nd edition 1804