Why did captain cook call Australia Australia?

Answer 1

Captain Cook did not call Australia Australia. He gave the name of New South Wales to the eastern coast of the continent.

Matthew Flinders, who was the first known European explorer to circumnavigate the Australian continent in 1802, is credited with assigning the name 'Australia' to this continent although it did not immediately receive universal approval. He first proposed the name "Terra Australis" be adopted instead of "New Holland", the name by which the Dutch knew Australia, or "New South Wales", which Cook had named the eastern half when he claimed it for England. In 1814 when Flinders published his work 'A Voyage to Terra Australis', he used the term 'Australia' within the book. Around 1818, Governor Lachlan Macquarie, arguably the most influential man in Australia at the time, also requested that the name "Australia" be officially ascribed.

The name 'Australia' was formally adopted in 1824.