The story
- Proto-Italic*wre-
- Latinre-
- Proto-Indo-European*terh₂-
- Proto-Indo-European*tr̥h₂dos
- Proto-Italic*tardos
- Latintardus
- Latinretardō
- Anglo-Normanretarder
- Middle Englishretarden
- English todayretard
From Middle English retarden, from Anglo-Norman retarder, from Latin retardō (“to retard”, from re- + tardus (“slow”)).
Etymology from Wiktionary, CC BY-SA 4.0.