halcyon: [14] Halcyon days, originally ‘days of calm weather’, but now used figuratively for a ‘past period of happiness and success’, are literally ‘days of the kingfisher’. The expression comes from Greek alkuonídes hēmérai ‘kingfisher’s days’, a term used in the ancient world for a period of 14 days fine or calm weather around the winter solstice which was attributed to the magical influence of the kingfisher. The origin of Greek alkúon is not known, although it was from earliest times associated with Greek háls ‘sea’ and kúōn ‘conceiving’ (whence the spelling halcyon). [halcyon etymology, halcyon origin, 英语词源]