Analysis of information sources in references of the Wikipedia article "Four Courts" in English language version.
Original historic use of the plural form: use of the singular form is a relatively new habit. Even at the beginning of the twentieth century, speakers had the choice of using the plural form also, and many survivals of that usage are seen at the present time, particularly in proper names: na Ceithre Cuirteanna, for example, is said, even though na Ceithre Chúirt would be more correct according to current language rules.
