nonaccent

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*h₂éd
15. Proto-Italic*ad
16. Proto-Italic*ad-
17. Latinad-
18. Proto-Indo-European*keh₂n-
19. Proto-Indo-European*kh₂néti
20. Proto-Italic*kanō
21. Latincanō
22. Latinaccinō
23. Ancient Greekπροσῳδῐ́ᾱ (prosōidĭ́ā)
24. Medieval Latinaccentus
25. Middle Frenchaccent
26. Anglo-Normanaccent
27. Middle Englishaccent
28. Englishaccent
29. English todaynonaccent

From non- + accent.