The story
- Proto-Indo-European*pós
- Proto-Indo-European*pósti
- Proto-Italic*posti
- Old Latinposte
- Latinpost
- Englishpost-
- Englishmillennial
- Englishpostmillennial
- English todaypostmillennialism
From postmillennial + -ism.
Etymology from Wiktionary, CC BY-SA 4.0.