From the Latin cardo 'hinge/pivot/pole', the term is used to denote something of foremost importance (hence cardinal sins, cardinal directions, cardinal rules, etc.). In astrology the angles are known as ‘cardinal points’; the angular houses are known as ‘cardinal houses’ and the signs of the equinoxes and solstices– Aries, Cancer, Libra and Capricorn –  are known as ‘cardinal signs’.