This is the 2779th most frequent Dutch word.
sint
"Saint" or "Sinterklaas" (Saint Nicholas).
In this context, "de Sint" signifies Saint Nicholas within the cultural tradition where children sing songs dedicated to him.
Heb je al liedjes voor de Sint geleerd?
Have you already learned songs for Saint Nicholas?
In this sentence, "Sint" refers to "Saint," as part of the figure Saint Nicholas, a legendary figure in Dutch culture associated with the holiday Sinterklaas.
Sint-Nicolaas komt ieder jaar op 5 december.
Saint Nicholas comes every year on December 5th.
Here, "de Sint" is a colloquial way to refer to Saint Nicholas, showing familiarity with the traditional figure.