The history and use of the term "moth hour"

Once upon a time in poor rural Ireland there were no such things as clocks. There were few ways to tell the passage of time except for a handful of naturally occurring events. One of those events, occurring nightly at dusk as the last bits of sun slipped away and each morning as the first rays of light broke out over the hills, the skies of the Irish countryside filled with hundreds if not thousands of moths. The moth-hour, while not a literal, formal unit of time, both makes reference to the time around dusk and dawn where moths filled the skies and to those who would measure their days with nature, not numbers.

The American poet Robert Penn Warren wrote the poem "I heard a voice at Moth-Hour" which uses the term to describe dusk. He also uses "dewfall" to mean early morning.

OED gives the first usage of 'moth-hour' as by Yeats in 'Countess Kathleen' (published 1892, but evidently composed 1890 as that's the date they give.)

Yeats may of course have borrowed it from hearing it used by country folk; but OED also indicates a connection with 'moth-time' a coinage found in the poetry of John Keats:

1820 Keats Lamia i, in Lamia & Other Poems 16 'Now on the moth-time of that evening dim/He would return that way.'

The possibility exists that Yeats got it from Keats.