Where does “Αυστραλία” come from?

Αυστραλία (Greek) comes from English Australia, from Latin terra austrālis incōgnita, from Latin auster, from Proto-Italic *austeros.

Ancestry of “Αυστραλία”, step by step

Step	Language	Word	Meaning
1	English	Australia	—
2	Latin	terra austrālis incōgnita	—
3	Latin	auster	The south wind; south
4	Proto-Italic	*austeros	—

Αυστραλία — Etymology, Origin & Word History | Etymology Explorer