origin of the word "cardinal"

I am still reading former San Francisco's archbishop John Quinn's book entitled Reforming the Papacy which was published in 1999, and I came across his description of the history of the word "cardinal."

The word comes from the Latin cardo which means "hinge." And so he writes, "The term 'cardinal' seems to go back to the massive relocation of peoples from Eastern into Western Europe in the sixth century. The term was originally used of bishops who were driven out of their dioceses by the invading tribes and whom Gregory I (590-604) appointed to other sees."

So, the idea is that these displaced bishops were "attached," as a door to a hinge, to a diocese other than the one for which they were ordained to serve. Then in later eras, the title was used by the Germanic people to refer to clergy who are under the direct supervision of a bishop and who are not serving in parishes, chapels, under noblemen, and others.

Then in Spain during the 11th century as well as in Germany, the use of the title was meant to describe clergy who served in a cathedral or a shrine. So, Quinn points out, "up to a certain point the title was not exclusively used in Rome. It is interesting to note that even to the present day, two canons of the Anglican St. Paul's Cathedral in London have the title 'cardinal.'"

The history of the use of the title is still reflected in today's practice of having cardinals serve at various cathedrals and basilicas in Rome. They are thus serving in basilicas and cathedrals other than those to which they were originally ordained to serve. Interesting.