Where does “eternally” come from?

Eternally comes from Middle English eternally, formed from the Middle English adverb-forming suffix -ly added to an adjective derived from Old English -līċ, ultimately from Latin aeternalis, composed of Latin aevum meaning "age" or "lifetime" with the Latin suffix -alis.

eternally (English): For eternity; forever; Unceasingly, recurringly

Definitions

  1. For eternity; forever; Unceasingly, recurringly

Ancestry of “eternally”, step by step

eternally traces back through two separate lines of ancestry.

via English eternal

StepLanguageWordMeaning
1EnglisheternalLasting forever; unending; existing outside time;...
2Middle EnglisheternalEternal, permanent; having existed forever;...
3Old Frencheternal
4Latinaeternāliseternal, everlasting, temporally infinite
5Latinaeternusabiding, lasting, permanent, perpetual; eternal,...
6Latinaevumtime as a single, unified, continuous and...
7LatinaevomArchaic form of aevum
8Old Latinaivomtime, lifetime; age
9Proto-Italicaiwomage
10Proto-Indo-Europeanh₂eyu-vitality; eternal; vital force, life, long life,...
11Proto-Indo-Europeanh₂ey-vital force, life, age, eternity; day, morning

via Middle English eternally

StepLanguageWordMeaning
1Middle EnglisheternallyIn an eternal, endless, or permanent manner; In a...
Every word from Proto-Indo-European h₂ey-
eternally — Etymology, Origin & Word History | Etymology Explorer