The Etymology of Eternal
Eternal has its roots in something mortal. The Latin aeternus ('everlasting') is a contraction of aeviternus, derived from aevum, which simply meant 'age' or 'lifetime' — a finite span, not an infinite one. The leap from a human lifespan to forever happened within Latin itself, as philosophers and poets stretched aevum to encompass cosmic time. The deeper Proto-Indo-European root *h₂eyu- meant 'vital force' or 'life span,' and its descendants scatter across the Indo-European family. Greek took it as aion (giving English eon and the theological concept of ages). Germanic languages produced the archaic aye ('forever'), still heard in 'for aye.' And Latin combined aevum with medius to create the adjective medievalis — 'of the middle age' — making medieval and eternal unexpected siblings. English borrowed eternal through Old French eternel in the 14th century, chiefly in religious contexts. The Eternal City (Rome) and eternal life were among its earliest uses.