To define the names of the eight territories of Australia seems a little pointless, for they are obvious. Of course, this is because they were named very recently, albeit from words often coined very much earlier. Yet these are worthwhile looking at for, unlike most names which simply developed, these were chosen.
Western Australia - obviously the westernmost part of Australia, but why 'west'? It transpires this an abbreviation of the Proto-Indo-European compound wes-pero meaning 'evening'. Australia is an abbreviation of the Latin Terra Australis meaning simply 'southern land'.
Southern Australia - from the Proto-Germanic sunthaz or quite literally 'sun side'. For the origins of Australia see Western Australia above.
Northern Territory - 'north' comes from Proto-Indo-European ner meaning 'left' as that is where north lies when facing the rising sun. Note the same word is the root of Sanskrit narakah 'hell'. Territory is ultimately from Proto-Indo-European ters 'to dry' and orium a suffix denoting place. Together this produced the Latin territorium meaning 'a place from which people are warned off'.
Australian Capital Territory - Named as such for it is home to Canberra, itself a greatly Anglicised version of an indigenous name. Tales of this being named Canberry because of the number of native Australian Cranberry bushes growing around here seems fanciful, at best. Possibly this represents an old Ngunnawal word meaning 'meeting place', although other sources point to the two mountains which dominate the skyline and thus the river running between them is the nganbira or 'hollow between a woman's breasts'. For the origins of Territory see Northern Territory above and for the origins of Australia see Western Australia, also above.
New South Wales - a word seen since Proto-Indo-European newo and thus has hardly changed in form or meaning for thousands of years. For the origins of south see South Australia above, while Wales is an Old English word, where wahl meant 'foreigner' or, more correctly, 'not Saxon'.
Queensland - named in 1859 after former monarch Queen Victoria.
Victoria - exactly as for Queensland above.
Tasmania - is named after the Dutch explorer Abel Tasman, the first European to sight the island, doing so on November 24th 1642, although he called it Van Diemen's Land after the then Dutch governor-general of the East Indies. Abel's surname comes from a Germanic term meaning 'of great faith'.
What do we know of the names of regional names used by those living here for millennia prior to the arrival of the Europeans? Nothing, as while they had names for places they did not name vast areas as they simply did not need to.