aurora borealis n.

"morning light, dawn," late 14c., from Latin Aurora, the Roman goddess of dawn, from PIE *ausus- "dawn," also the name of the Indo-European goddess of the dawn, from root *aus- (1) "to shine," especially of the dawn (source also of Greek ēōs "dawn").

"northern," late 15c., from Late Latin borealis, from Latin Boreas "north wind," from Greek Boreas, name of the god of the north wind, which is of unknown origin, perhaps related to words in Sanskrit (giri-) and Balto-Slavic (Lithuanian girė, Old Church Slavonic gora) for "mountain" (also "forest") as if "those living beyond the mountains."

1790, shortening of aurora borealis (q.v.).