This is from *rkto-, the usual Indo-European root for "bear" (source also of Avestan aresho, Armenian arj, Albanian ari, Latin ursus, Welsh arth); see bear (n.) for speculation on why Germanic lost the word.
The -c- was restored from 1550s. From early 15c. as "northern;" from 1660s as "cold, frigid." As a noun, with capital A-, "the northern polar regions," from 1560s.
1550s in astronomy, in reference to a celestial circle, a line around the sky which, in any location, bounds the stars which are ever-visible from that latitude (in the Northern Hemisphere its center point is the celestial north pole); the concept goes back to the ancient Greeks, for whom this set of constellations included most prominently the two bears (arktoi), hence the name for the circle (see arctic). In Middle English it was the north cercle (late 14c.).
In geography, from 1620s as "the circle roughly 66 degrees 32 minutes north of the equator" (based on obliquity of the ecliptic of 23 degrees 28 minutes), marking the southern extremity of the polar day, when the sun at least theoretically passes the north point without setting on at least one summer day and does not rise on at least one winter one.
late 14c., orange bright star in the constellation Bootes (also used of the whole constellation), from Latin Arcturus, from Greek Arktouros, literally "guardian of the bear" (the bright star was anciently associated with nearby Ursa Major, the "Big Dipper," which it seems to follow across the sky). For first element see arctic; second element is Greek ouros "watcher, guardian, ward," from PIE root *wer- (3) "perceive, watch out for." It is fourth-brightest of the fixed stars. The double nature of the great bear/wagon (see Big Dipper) has given two different names to the constellation that follows it: Arktouros "bear-ward" and Bootes "the wagoner" (from Greek, ultimately from PIE root *gwou- "ox, bull, cow").
Arcturus in the Bible (Job ix.9 and xxxviii.32) is a mistranslation by Jerome (continued in KJV) of Hebrew 'Ayish, which refers to what we see as the "bowl" of the Big Dipper. In Israel and Arabia, the seven stars of the Great Bear seem to have been a bier (the "bowl") followed by three mourners. In the Septuagint it was translated as Pleiada, which is equally incorrect.
"large carnivorous or omnivorous mammal of the family Ursidae," Old English bera "a bear," from Proto-Germanic *bero, literally "the brown (one)" (source also of Old Norse björn, Middle Dutch bere, Dutch beer, Old High German bero, German Bär), usually said to be from PIE root *bher- (2) "bright; brown." There was perhaps a PIE *bheros "dark animal" (compare beaver (n.1) and Greek phrynos "toad," literally "the brown animal").
Greek arktos and Latin ursus retain the PIE root word for "bear" (*rtko; see arctic), but it is believed to have been ritually replaced in the northern branches because of hunters' taboo on names of wild animals (compare the Irish equivalent "the good calf," Welsh "honey-pig," Lithuanian "the licker," Russian medved "honey-eater"). Others connect the Germanic word with Latin ferus "wild," as if it meant "the wild animal (par excellence) of the northern woods."
Symbolic of Russia since 1794. Used of rude, gruff, uncouth men since 1570s. Stock market meaning "speculator for a fall" is 1709 shortening of bearskin jobber (from the proverb sell the bearskin before one has caught the bear); i.e. "one who sells stock for future delivery, expecting that meanwhile prices will fall." Paired with bull from c. 1720. Bear claw as a type of large pastry is from 1942, originally chiefly western U.S. Bear-garden (1590s) was a place where bears were kept for the amusement of spectators.
Old English Carles wægn, a star-group associated in medieval times with Charlemagne, but originally with the nearby bright star Arcturus, which is linked by folk etymology to Latin Arturus "Arthur." Which places the seven-star asterism at the crux of the legendary association (or confusion) of Arthur and Charlemagne. Evidence from Dutch (cited in Grimm, "Teutonic Mythology") suggests that it might originally have been Woden's wagon. More recent names for it are the Plough (by 15c., chiefly British) and the Dipper (1833, chiefly American).
It is called "the Wagon" in a Mesopotamian text from 1700 B.C.E., and it is mentioned in the Biblical Book of Job. The seven bright stars in the modern constellation Ursa Major have borne a dual identity in Western history at least since Homer's time, being seen as both a wagon and a bear: as in Latin plaustrum "freight-wagon, ox cart" and arctos "bear," both used of the seven-star pattern, as were equivalent Greek amaxa (Attic hamaxa) and arktos.
The identification with a wagon is easy to see, with four stars as the body and three as the pole. The identification with a bear is more difficult, as the figure has a tail longer than its body. As Allen writes, "The conformation of the seven stars in no way resembles the animal,--indeed the contrary ...." But he suggests the identification "may have arisen from Aristotle's idea that its prototype was the only creature that dared invade the frozen north." The seven stars never were below the horizon in the latitude of the Mediterranean in Homeric and classical times (though not today, due to precession of the equinoxes). See also arctic for the identification of the bear and the north in classical times.
A variety of French and English sources from the early colonial period independently note that many native North American tribes in the northeast had long seen the seven-star group as a bear tracked by three hunters (or a hunter and his two dogs).
Among the Teutonic peoples, it seems to have been only a wagon, not a bear. A 10c. Anglo-Saxon astronomy manual uses the Greek-derived Aretos, but mentions that "unlearned men" call it "Charles's Wain":
Arheton hatte an tungol on norð dæle, se haefð seofon steorran, & is for ði oþrum naman ge-hatan septemtrio, þone hatað læwede meon carles-wæn. ["Anglo-Saxon Manual of Astronomy"]
[Septemtrio, the seven oxen, was yet another Roman name.] The star picture was not surely identified as a bear in English before late 14c.
The unlearned of today are corrected that the seven stars are not the Great Bear but form only a part of that large constellation. But those who applied the name "Bear" apparently did so originally only to these seven stars, and from Homer's time down to Thales, "the Bear" meant just the seven stars. From Rome to Anglo-Saxon England to Arabia to India, ancient astronomy texts mention a supposed duplicate constellation to the northern bear in the Southern Hemisphere, never visible from the north. This perhaps is based on sailors' tales of the Southern Cross.