noncolloquial

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. Proto-Indo-European*telkʷ-
20. Proto-Indo-European*tlokʷetor
21. Proto-Italic*tlokʷōr
22. Latinloquor
23. Latincolloquor
24. Latincolloquium
25. Middle Englishcolloquies
26. Englishcolloquy
27. Proto-Indo-European*h₂el-
28. Proto-Indo-European*h₂élisder.?
29. Englishcolloquial
30. English todaynoncolloquial

From non- + colloquial.