Word Origin & History
1545, in halcyon dayes (L. alcyonei dies, Gk. alkyonides hemerai), 14 days of calm weather at the winter solstice, when a mythical bird (identified with the kingfisher) was said to breed in a nest floating on calm seas. From halcyon (n.), 1390, from L. halcyon, from Gk. halkyon, variant (perhaps a misspelling)
of alkyon "kingfisher," from hals "sea, salt" + kyon "conceiving," prp. of kyein "to conceive," lit. "to swell," from PIE base *keue- "to swell." Identified in mythology with Halcyone, daughter of Aeolus, who when widowed threw herself into the sea and became a kingfisher.