The story
- Proto-Indo-European*per-der.?
- Proto-Indo-European*pér
- Proto-Indo-European*pró
- Proto-Italic*prō
- Latinprō
- Englishpro-
- Proto-Indo-European*bʰeydʰ-
- Proto-Indo-European*bʰeydʰós
- Proto-Italic*feiðos
- Latinfoedus
- Proto-Indo-European*h₂el-
- Proto-Indo-European*h₂élisder.?
- Frenchfédéra
- Englishfederal
- Englishfederalist
- English todaypro-federalist
From pro- + federalist.
Etymology from Wiktionary, CC BY-SA 4.0.