During the Middle Ages, Christmas peace was always announced in the evening on Christmas Eve and stretched for 20 days. Christmas holidays meant that it became more expensive to commit crimes. According to Wikipedia, the normal fine for killing 26,000 marks, half went to the king and half to the city, but when Christmas peace was announced, it cost an extra 3 marks, money that went to the bishop because the crime was committed on a Christian weekend.
The Christmas holidays in Söderköping are not related to any cost of death, but to the fact that during Christmas there should be peaceful and friendly people between.
See the video with Erik Nilsson above in connection with the announcement of Christmas holidays in Söderköping 2019.