... and the cows have tails ...

.... Is a phrase out of the songs at St. Martin's Day, also known as the Feast of St. Martin or Martinmas or St Martin of Tours or Martin le Miséricordieux.
The day is celebrated on the evening of November 11 in some parts of the Netherlands, where it is known as Sint Maarten.
It celebrates the end of the agrarian year and the beginning of the harvesting. At St. Martin's eve, people ate and drank very heartily for a last time before they started to fast.

St. Martin was known as friend of the children and patron of the poor
As soon it gets dark, children up to the age of 11/12 (primary school age) go door to door with hand-crafted paper lanterns, singing songs like "Sinte Sinte Maarten" hoping to receive some candy or fruit in return.