late 14c., "quality of being eternal," from Old French eternité "eternity, perpetuity" (12c.), from Latin aeternitatem (nominative aeternitas), from aeternus "enduring, permanent" (see eternal). Meaning "infinite time" is from 1580s. In the Mercian hymns, Latin aeternum is glossed by Old English ecnisse.[eternity etymology, eternity origin, 英语词源]