nondifferent

The story

1. Proto-Indo-European*né
2. Proto-Germanic*ne
3. Proto-Indo-European*ís?
4. Proto-Indo-European*h₁óynos
5. Proto-Germanic*ainaz
6. Proto-Germanic*nainaz
7. Proto-West Germanic*nain
8. Old Englishnān
9. Middle Englishnon
10. Old Englishnān
11. Old Englishnān-
12. Middle Englishnon-
13. Englishnon-
14. Proto-Indo-European*dwóh₁
15. Proto-Indo-European*trísinflu.
16. Proto-Indo-European*d(w)is-
17. Proto-Italic*dis-
18. Latindis-
19. Proto-Indo-European*bʰer-
20. Proto-Indo-European*bʰéreti
21. Proto-Italic*ferō
22. Latinferō
23. Latindifferō
24. Latindifferēns
25. Old Frenchdifferent
26. Middle Englishdifferent
27. Englishdifferent
28. English todaynondifferent

From non- + different.