1877, from German, literally "eternity."
Online Etymology Dictionary, © 2010 Douglas Harper
Examples from the Web for ewigkeit
All we know is that they flew into the Ewigkeit and are "missing."Cavalry of the Clouds
Those found, he goes off with ponderous serenity into the ewigkeit.
Her determination of two hours ago had vanished into the Ewigkeit.Golden Stories
Ewigkeit was therefore originally time, and “for all time” came naturally to mean “for all eternity.”My Autobiography
F. Max Mller
When another week has rolled by and disappeared into the Ewigkeit, vary the menu.The Feasts of Autolycus
Elizabeth Robins Pennell