The story
- Proto-Indo-European*dwóh₁
- Proto-Indo-European*trísinflu.
- Proto-Indo-European*d(w)is-
- Proto-Italic*dis-
- Latindis-
- Proto-Indo-European*bʰer-
- Proto-Indo-European*bʰéreti
- Proto-Italic*ferō
- Latinferō
- Latindifferō
- Latindifferēns
- Old Frenchdifferent
- Middle Englishdifferent
- Englishdifferent
- Englishability
- English todaydiffability
Blend of different + ability, as a play on disability intended to remove the term's negative connotations.
Etymology from Wiktionary, CC BY-SA 4.0.