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angular (adj.)[angular 词源字典]: 1590s, from Latin angularis "having corners or angles," from angulus (see angle (n.)). Earlier in an astrological sense, "occupying a cardinal point of the zodiac" (late 14c.). Angulous "having many corners" is from mid-15c.[angular etymology, angular origin, 英语词源]
cardinal (adj.): "chief, pivotal," early 14c., from Latin cardinalis "principal, chief, essential," from cardo (genitive cardinis) "that on which something turns or depends; pole of the sky," originally "door hinge," which is of unknown origin. Related: Cardinally.

The cardinal points (1540s) are north, south, east, west. The cardinal sins (c. 1600) are too well known to require rehearsal. The cardinal virtues (c. 1300) were divided into natural (justice prudence, temperance, fortitude) and theological (faith, hope, charity). The natural ones were the original classical ones, which were amended by Christians. But typically in Middle English only the first four were counted as the cardinal virtues:
Of þe uour uirtues cardinales spekeþ moche þe yealde philosofes. ["Ayenbite of Inwyt," c. 1340]
By analogy of this, and cardinal points, cardinal winds, cardinal signs (four zodiacal signs marking the equinoxes and the solstices), the adjective in Middle English acquired an association with the number four.
east: Old English east, eastan (adj., adv.) "east, easterly, eastward;" easte (n.), from Proto-Germanic *aust- "east," literally "toward the sunrise" (cognates: Old Frisian ast "east," aster "eastward," Dutch oost Old Saxon ost, Old High German ostan, German Ost, Old Norse austr "from the east"), from PIE *aus- (1) "to shine," especially of the dawn (cognates: Sanskrit ushas "dawn;" Greek aurion "morning;" Old Irish usah, Lithuanian auszra "dawn;" Latin aurora "dawn," auster "south;" see aurora). The east is the direction in which dawn breaks. For theory of shift in the geographical sense in Latin, see Australia.

As one of the four cardinal points of the compass, from c. 1200. Meaning "the eastern part of the world" (from Europe) is from c. 1300. Cold War use of East for "communist states" first recorded 1951. French est, Spanish este are borrowings from Middle English, originally nautical. The east wind in Biblical Palestine was scorching and destructive (as in Ezek. xvii:10); in New England it is bleak, wet, unhealthful. East End of London so called by 1846; East Side of Manhattan so called from 1871; East Indies (India and Southeast Asia) so called 1590s to distinguish them from the West Indies.
south (adv.): Old English suð "southward, to the south, southern, in the south," from Proto-Germanic *sunthaz, perhaps literally "sun-side" (cognates: Old Saxon, Old Frisian suth "southward, in the south," Middle Dutch suut, Dutch zuid, German Süden), and related to base of *sunnon "sun" (see sun (v.)). Old French sur, sud (French sud), Spanish sur, sud are loan-words from Germanic, perhaps from Old Norse suðr.

As an adjective from c. 1300; as a noun, "one of the four cardinal points," also "southern region of a country," both late 13c. The Southern states of the U.S. have been collectively called The South since 1779 (in early use this often referred only to Georgia and South Carolina). South country in Britain means the part below the Tweed, in England the part below the Wash, and in Scotland the part below the Forth. South Sea meant "the Mediterranean" (late 14c.) and "the English Channel" (early 15c.) before it came to mean (in plural) "the South Pacific Ocean" (1520s). The nautical coat called a sou'wester (1836) protects the wearer against severe weather, such as a gale out of the southwest.