cardinal: [12] The ultimate source of cardinal is Latin cardō ‘hinge’, and its underlying idea is that something of particular, or ‘cardinal’, importance is like the hinge on which all else depends. English first acquired it as a noun, direct from ecclesiastical Latin cardinālis (originally an adjective derived from cardō), which in the early church denoted simply a clergyman attached to a church, as a door is attached by hinges; it only gradually rose in dignity to refer to princes of the Roman Catholic church. The adjective reached English in the 13th century, via Old French cardinal or Latin cardinālis. [cardinal etymology, cardinal origin, 英语词源]