Today’s word is sempiternal.
The word means eternal and unchanging; everlasting. Its origins are from Late Middle English: from Old French sempiternel or late Latin sempiternalis, from Latin sempiternus, from semper ‘always’ + aeternus ‘eternal’.
But in philosophy there is a distinction between eternal and sempiternal. Eternal implies something that is infinite outside the bounds of time, like God, while sempiternal is a more earthbound way to talk about forever.
“The one thing which we seek with insatiable desire is to forget ourselves, … to lose our sempiternal memory, and to do something without knowing how or why….”– Ralph Waldo Emerson