eo-

Early, primeval.

Greek ēōs, dawn.

The Eocene geological period is the second epoch of the Tertiary period, between the Palaeocene and Oligocene epochs; the eohippus (Greek hippos, horse) is an older name for the hyracotherium, the earliest fossil ancestor of the horse; Eoanthropus (Greek anthrōpos, human being, so ‘dawn man’) is the genus to which the now-discredited Piltdown man was assigned; an eolith (Greek lithos, stone) is a roughly chipped flint found in Tertiary strata, originally thought to be an early artefact but probably of natural origin. The red fluorescent dye eosin uses the Greek literally, since its colour was thought to resemble a reddish sunrise; derived from this is eosinophil, a white blood cell containing granules that are readily stained by eosin, plus several other terms. Eolian, however, is the standard US spelling of British English aeolian, relating to or arising from the action of the wind, from Greek Aiolos, the god of the winds.