nonrhythmic

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*ser-?
15. Proto-Indo-European*srew-
16. Proto-Indo-European*sru-dʰ-mo-s
17. Proto-Hellenic*hrutʰmós
18. Ancient Greekῥῠθμός (rhŭthmós)
19. Ancient Greekῥυθμικός (rhuthmikós)
20. Englishrhythmic
21. English todaynonrhythmic

From non- + rhythmic.