1911 Encyclopædia Britannica/Aeon

AEON, a term often used in Greek (αἰών) to denote an indefinite or infinite duration of time; and hence, by metonymy, a being that exists for ever. In the latter sense it was chiefly used by the Gnostic sects to denote those eternal beings or manifestations which emanated from the one incomprehensible and ineffable God. (See Gnosticism.)