noncoherent

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*ḱe?
15. Proto-Indo-European*ḱóm
16. Proto-Italic*kom
17. Proto-Italic*kom-
18. Latincon-
19. Latinhaereō
20. Latincohaereō
21. Latincohaerēns
22. Middle Frenchcoherent
23. Englishcoherent
24. English todaynoncoherent

From non- + coherent.