arctic:  Etymologically, the Arctic is the region of the ‘bear’. Nothing to do with polar bears, though. The characteristic constellations of the northern hemisphere are the ‘Little Bear’ (Latin Ursa Minor), which contains the northern celestial pole, and the Plough, otherwise known as the ‘Great Bear’ (Latin Ursa Major). The perception that they resemble a bear (Greek arktos) goes back to ancient times, and the Greeks used the derived adjective arktikos, literally ‘relating to bears’, to denote ‘northern’.
By the time this reached English, via Latin ar(c)ticus and Old French artique, it was being applied specifically to the northern polar regions. (The original English spelling, reflecting the French form, was artic. The more etymologically ‘correct’ arctic came in in the 17th century, but uncertain spellers are still apt to regress to artic.) Antarctic  for the corresponding southern polar region likewise comes ultimately from Greek (antarktikos, with the prefix anti- ‘opposite’). Arcturus , the name of a very bright star in the constellation Boötes, means literally ‘bear watcher’ or ‘bear guardian’ (Greek Arktouros), a reference to the fact that the tail of the Great Bear points towards it.
late 14c., artik, from Old French artique, from Medieval Latin articus, from Latin arcticus, from Greek arktikos "of the north," literally "of the (constellation) Bear," from arktos "bear; Ursa Major; the region of the north," the Bear being a northerly constellation. From *rkto-, the usual Indo-European base for "bear" (cognates: Avestan aresho, Armenian arj, Albanian ari, Latin ursus, Welsh arth); see bear (n.) for why the name changed in Germanic. The -c- was restored from 1550s. As a noun, "the Arctic regions," from 1560s.