monodesethyl

The story

1. Proto-Indo-European*men-
2. Proto-Hellenic*mónwos
3. Ancient Greekμόνος (mónos)
4. Ancient Greekμονο- (mono-)
5. Englishmono-
6. Proto-Indo-European*dwóh₁
7. Proto-Indo-European*trísinflu.
8. Proto-Indo-European*d(w)is-
9. Proto-Italic*dis-
10. Latindis-
11. Old Frenchdes-
12. Latindis-
13. Middle Englishdes-
14. Englishdes-
15. Proto-Indo-European*h₂eydʰ-
16. Proto-Hellenic*áitʰō
17. Ancient Greekαἴθω (aíthō)
18. Ancient Greekᾱ̓ήρ (āḗr)influ.?
19. Ancient Greekαἰθήρ (aithḗr)
20. Latinaethēr
21. GermanÄther
22. GermanEther
23. Proto-Indo-European*swel-der.?
24. Ancient Greekῡ̔́λη (hū́lē)
25. GermanEthy
26. Englishethyl
27. Englishdesethyl
28. English todaymonodesethyl

From mono- + desethyl.