The word halcyon comes from a story in Greek mythology about the halcyon bird, which had the power to calm the rough ocean waves every December so she could nest. Like those calm waters, halcyon has come to mean a sense of peace or tranquillity. People often use the phrase halcyon days to refer idyllically to a calmer, more peaceful time in their past.
Although the Halcyon is a bird of Greek legend, the name is now commonly given to the European Kingfisher. The ancients believed that the bird made a floating nest in the Aegean Sea and had the power to calm the waves while brooding her eggs. Fourteen days of calm weather were to be expected when the Halcyon was nesting – around the winter solstice, usually 21st or 22nd of December. The Halcyon days are generally regarded as beginning on the 14th or 15th of December.
The source of the belief in the bird’s power to calm the sea originated in a myth recorded by Ovid. The story goes that Aeolus, the ruler of the winds, had a daughter named Alcyone, who was married to Ceyx, the King of Thessaly. Ceyx was drowned at sea and Alcyone threw herself into the waves in a fit of grief. Instead of drowning, she was transformed into a bird and carried to her husband by the wind.