The story
- Proto-Indo-European*h₁reh₁p-
- Proto-Indo-European*h₁r̥h₁pyéti
- Proto-Italic*rapjō
- Latinrapiō
- Proto-Indo-European*dʰeh₁-
- Latinrapidus
- Middle Frenchrapide
- Latinrapidus
- English todayrapid
Borrowed from Middle French rapide and its etymon Latin rapidus.
Etymology from Wiktionary, CC BY-SA 4.0.