nonlinearly

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*līnom
15. Proto-Italic*līnom
16. Latinlīnum
17. Latinlīneus
18. Latinlīnea
19. Proto-Indo-European*h₂el-
20. Proto-Indo-European*h₂élisder.?
21. Latinlīneāris
22. Englishlinear
23. Englishnonlinear
24. Proto-Indo-European*leyg-
25. Proto-Germanic*līką
26. English todaynonlinearly

From nonlinear + -ly.