Webster's Revised Unabridged Dictionary · 1913

Halcyon

Halcyon (hal"si*on) , noun

[Latin halcyon, alcyon, Greek "alkyw`n, 'alkyw`n: compare French halcyon.]

(Zoology) A kingfisher. By modern ornithologists restricted to a genus including a limited number of species having omnivorous habits, as the sacred kingfisher (Halcyon sancta) of Australia.
Amidst our arms as quiet you shall be As halcyons brooding on a winter sea. — Dryden

Halcyon , adjective

1.
Pertaining to, or resembling, the halcyon, which was anciently said to lay her eggs in nests on or near the sea during the calm weather about the winter solstice.
2.
Hence: Calm; quiet; peaceful; undisturbed; happy.
Deep, halcyon repose. — De Quincy