septentrion n.

"1 more than six; the cardinal number which is one more than six; a symbol representing this number;" Old English seofon, from Proto-Germanic *sebun (source also of Old Saxon sibun, Old Norse sjau, Swedish sju, Danish syv, Old Frisian sowen, siugun, Middle Dutch seven, Dutch zeven, Old High German sibun, German sieben, Gothic sibun), from PIE *septm "seven" (source also of Sanskrit sapta, Avestan hapta, Hittite shipta, Greek hepta, Latin septem, Old Church Slavonic sedmi, Lithuanian septyni, Old Irish secht, Welsh saith).

Long regarded as a number of perfection (seven wonders; seven sleepers, the latter translating Latin septem dormientes; seven against Thebes, etc.), but that notion is late in Old English and in German a nasty, troublesome woman could be eine böse Sieben "an evil seven" (1662). Magical power or healing skill associated since 16c. with the seventh son ["The seuenth Male Chyld by iust order (neuer a Gyrle or Wench being borne betweene)," Thomas Lupton, "A Thousand Notable Things," 1579]. The typical number for "very great, strong," as in seven-league boots in the fairy story of Hop o'my Thumb. Also, formerly, in combination with days, years, etc., indicating merely a very long time.

By early 15c. as "the hour of 7 o'clock." As a high-stakes number for a throw in dice, late 14c. The Seven Years' War (1756-63) is also the Third Silesian War. The Seven Stars (Old English sibunsterri), usually refers to the Pleiades, though in 15c. and after this name occasionally was given to the Big Dipper (which also has seven stars), or the seven planets of classical astronomy. Popular as a tavern sign, it might also (with six in a circle, one in the center) be a Masonic symbol.

FOOL: ... The reason why the seven stars are no more than seven is a pretty reason.

LEAR: Because they are not eight?

FOOL: Yes, indeed: thou wouldst make a good fool.

["King Lear," I.v.]

*terə-, Proto-Indo-European root meaning "to rub, turn," with derivatives referring to twisting, also to boring, drilling, piercing; and to the rubbing of cereal grain to remove the husks, and thus to threshing.

It forms all or part of: atresia; attorn; attorney; attrition; contour; contrite; detour; detriment; diatribe; drill (v.) "bore a hole;" lithotripsy; return; septentrion; thrash; thread; thresh; throw; threshold; trauma; trepan; tribadism; tribology; tribulation; trite; triticale; triturate; trout; trypsin; tryptophan; turn.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit turah "wounded, hurt;" Greek teirein "to rub, rub away;" Latin terere "to rub, thresh, grind, wear away," tornus "turning lathe;" Old Church Slavonic tiro "to rub;" Lithuanian trinu, trinti "to rub," Old Irish tarathar "borer," Welsh taraw "to strike."

famous seven-star figure of the northern sky, Old English Carles wægn, a star-group associated in medieval times with Charlemagne, but earlier with the nearby bright star Arcturus. Arcturus 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 (not so 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. A 10c. Anglo-Saxon astronomy manual uses the Greek-derived Aretos, but mentions that the unlearned 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 only a part of that large constellation. But the name "Bear" belongs to the seven stars, and from Homer's time down to Thales, "the Bear" meant just that, but modern astronomers drew it bigger in parceling out the sky for their convenience.

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.