The name
Halcyon (n.) - from the Greek alkyon: the kingfisher believed to calm the sea for the fourteen days each winter it nested upon the water.
Sailors called those weeks the halcyon days. The only stretch of the year they trusted the water enough to sail.
We didn't take the name for the calm. We took it for the work behind it - someone had charted exactly when the sea would hold, long before anyone set out.
Not optimism. Certainty, earned in advance.