/
ˈhalsɪən, 
-ʃ(ə)n/
adj.
 denoting a past time regarded as idyllically happy and peaceful:
 the halcyon days of the mid 1980s.
n.
  - a mythical bird said to breed in a nest floating at sea, charming the wind and waves into calm.
 - a tropical Asian and African kingfisher with brightly coloured plumage. 
[Genus Halcyon: many species.]
 
Etymology
ME: via L. from Gk alkuōn ‘kingfisher’ (also halkuōn, by assoc. with hals ‘sea’ and kuōn ‘conceiving’).