The story
- Proto-Indo-European*(H)reh₁-
- Proto-Indo-European*(H)reh₁ís
- Proto-Italic*reis
- Latinrēs
- Proto-Italic*poplos
- Old Latinpoplus
- Old Latinpoplicus
- Latinpūblicus
- Latinpūblica
- Latinrēspūblica
- Latinrēpūblicā
- Middle Frenchrepublique
- English todayrepublic
From Middle French republique (“republic”), from Latin rēspūblicā, from rēs (“thing”) + pūblica (“public”); hence literally “the public thing”. Like with real, to many, the first morpheme has assimilated to re-, making it derivable as re- + public. Displaced native Old English cynewīse (“state, nation, republic”).
Etymology from Wiktionary, CC BY-SA 4.0.