'australasian' originates from Modern Latin, specifically from the geographical name 'Australasia', where 'austral-' meant 'southern' (from Latin 'australis') and 'Asia' referred to the continent 'Asia'.

'australasian' was formed in English by adding the adjectival suffix '-an' to 'Australasia' (a 19th-century coinage combining 'austral' + 'Asia'), producing the modern English adjective and noun 'australasian'.

Initially it meant 'of or relating to Australasia' as a geographic label; over time its use extended to refer specifically to peoples, flora, fauna, and cultural features of Australia, New Zealand, and nearby islands.