The story
- Proto-Indo-European*né
- Proto-Indo-European*n̥-
- Proto-Germanic*un-
- Proto-West Germanic*un-
- Old Englishun-
- Middle Englishun-
- Englishun-
- Proto-Germanic*raidō
- Proto-West Germanic*raidu
- Old Englishrād
- Middle Englishrode
- Englishroad
- Englishroadworthy
- English todayunroadworthy
From un- + roadworthy.
Etymology from Wiktionary, CC BY-SA 4.0.