From translingual Ephemeridae, from New Latin ephemerus, from Ancient Greek ἐφήμερος (ephḗmeros), the more common form of ἐφημέριος (ephēmérios, “of, for, or during the day, living or lasting but for a day, short-lived, temporary”), from ἐπί (epí, “on”) + ἡμέρα (hēméra, “day”).