The story
- Proto-Indo-European*né
- Proto-Indo-European*n̥-
- Proto-Italic*n̥-
- Latinin-
- Latindisputo
- Latindisputābilis
- Latinindisputābili
- Englishindisputable
- English todayindisputableness
From indisputable + -ness.
Etymology from Wiktionary, CC BY-SA 4.0.