Where does “antemillennial” come from?

antemillennial (English) comes from English millennial, from Late Latin millennium, from Latin -ennium, from Latin -ennis, from Latin annus, from Proto-Italic atnos, from Proto-Indo-European h₂et-no-, from Proto-Indo-European h₂et- — grass.

Ancestry of “antemillennial”, step by step

antemillennial traces back through two separate lines of ancestry.

via English millennial

StepLanguageWordMeaning
1EnglishmillennialReferring to the 1,000th anniversary of an event...
2Late Latinmillenniummillennium
3Latin-enniumforming periods of years
4Latin-ennis
5Latinannusyear; time; season
6Proto-Italicatnosyear
7Proto-Indo-Europeanh₂et-no-
8Proto-Indo-Europeanh₂et-grass

via English ante

StepLanguageWordMeaning
1EnglishanteA price or cost, as in up the ante; In poker and...
2Latinantebefore, in front, forwards; before; before,...
3Ancient Greekκλίσιςbending, inclination; a lying down; a place for...
4Ancient Greek-σῐς"suffix forming nouns"
5Ancient Greek-τιςretained after dentals
6Proto-Indo-European-tisDerives abstract/action nouns from verb roots
Every word from Proto-Indo-European h₂et-
antemillennial — Etymology, Origin & Word History | Etymology Explorer