As an adjective, “halcyon” is used in connection with an idealized version of the past. For example, remembering the halcyon days of yesteryear can bring about a nostalgia for better times. The noun form displays deep roots in Greek mythology. “Halcyon” comes from the story of the goddess Alcyone and her dear husband, who were turned into birds upon their deaths. These birds would only build nests in the sea on calm water, leading to the reputation of happy, peaceful days. The mythical birds were reportedly kingfishers, or halcyons, a real species of tropical bird.