equal + night = equinox
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equinox late 14c., from O.Fr. equinoce (12c.) or directly from M.L. equinoxium “equality of night (and day),” from L. aequinoctium “the equinoxes,” from aequus “equal” (see equal) + nox (gen. noctis) “night.” The O.E. translation was efnniht. Related: Equinoctial.
Seasonal change is definitely in the air (together with tens and tens of thousands of Canada geese massing for migration—as I noted this morning en route to work), on this special twice-a-year day on which the day’s minutes of daylight equal the minutes of darkness everywhere on our wee planet.
Autumnal up here in the North, Vernal down under… regardless, best equinoctial wishes to dear friends and colleagues far and near!