nonaccelerating

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*kel-
19. Latinceler
20. Latincelerō
21. Latinaccelerō
22. Latinaccelerātu
23. Latinaccelerō
24. Latinaccelerātiō
25. Englishaccelerationbf.
26. Englishaccelerating
27. English todaynonaccelerating

From non- + accelerating.