Semlor is traditionally eaten on Fat Tuesday, known as Fettisdagen in Swedish. The celebration of this day originates from the Christian tradition of Shrove Tuesday, marking the beginning of a 40-day fasting period before Easter. The calorie-heavy Semla was simply eaten as a way to prepare for fasting. The first mentions of Semlor are made in the bible of Gustav Vasa, the first king of Sweden. During the 18th century another Swedish king, Adolf Fredric, died after devouring 14 Semlor in just one sitting (following a five-course meal).