The story
- Proto-Indo-European*h₁rewdʰ-
- Old Englishrudu
- Old Englishrudiġ
- Middle Englishrody
- English todayruddy
Inherited from Middle English rody, from Old English rudiġ (“reddish; ruddy”), from rudu + -iġ. By surface analysis, rud (“redness”) + -y. Compare Icelandic roði (“redness”). The British slang sense expressing irritation is presumably a euphemism for bloody.
Etymology from Wiktionary, CC BY-SA 4.0.