Halcyon is a name for a bird of Greek legend which is commonly associated with the kingfisher. The phrase, Halcyon Days, comes from the ancient belief that fourteen days of calm weather were to be expected around the winter solstice - usually 21st or 22nd of December in the Northern Hemisphere. as that was when the halcyon calmed the surface of the sea in order to brood her eggs on a floating nest. The Halcyon days are generally regarded as beginning on the 14th or 15th of December. Now Halcyon is the name of a genus of Kingfisher, comprising of 11 species from Asia and Africa. (I've managed to see eight of them so far).
In English Halcyon means calm and tranquil, or 'happy or carefree'. It is rarely used now apart from in the expression halcyon days. The first time it was used this way may have been in Henry VI, 1599, Shakespeare refers to halcyon days:
JOAN LA PUCELLE:
Assign'd am I to be the English scourge.
This night the siege assuredly I'll raise:
Expect Saint Martin's summer, halcyon days,
Since I have entered into these wars.
Unfortunately Kingfishers are rare in the village, although there are records of one in the Bay in winter, when they tend to move away from their breeding areas.