halcyon [LME] The halcyon was a bird that in medieval times was thought to breed in a nest floating on the sea, and to charm the wind and waves so that the sea was calm. It was identified as a kingfisher, most of which actually nest in riverbanks, and the word comes from the Greek term for a kingfisher, alkuōn. The halcyon days [M16th] were originally 14 days of calm weather which were supposed to occur when the halcyon was breeding. Today the phrase refers to a period of time in the past that was idyllically happy and peaceful, as in ‘those halcyon days when students received full government grants’.