'Na Ceithre Chúirt,' and yet the lady calling out the names of the tram stops says 'Na Ceithre Cúirteanna' as we approach the Four Courts.

From the wikipedia 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 ... though na Ceithre Chúirt would be more correct according to current language rules.

Just been googling “pedantry” as gaeilge.