hydroxyethyl

The story

1. Proto-Indo-European*wed-
2. Proto-Indo-European*wódr̥
3. Proto-Hellenic*údōr
4. Ancient Greekῡ̆̔́δωρ (hū̆́dōr)
5. Ancient Greekὑδρο- (hudro-)
6. Frenchhydro-
7. Proto-Indo-European*ǵenh₁-
8. Proto-Indo-European*ǵénh₁os
9. Proto-Hellenic*génos
10. Ancient Greekγένος (génos)
11. Frenchhydrogène
12. Englishhydrogen
13. Proto-Indo-European*h₂eḱ-der.?
14. Ancient Greekὀξύς (oxús)
15. Ancient Greekγένος (génos)
16. Frenchoxygène
17. Englishoxygen
18. Proto-Indo-European*swel-der.?
19. Ancient Greekῡ̔́λη (hū́lē)
20. Englishhydroxyl
21. Englishhydroxy-
22. Proto-Indo-European*h₂eydʰ-
23. Proto-Hellenic*áitʰō
24. Ancient Greekαἴθω (aíthō)
25. Ancient Greekᾱ̓ήρ (āḗr)influ.?
26. Ancient Greekαἰθήρ (aithḗr)
27. Latinaethēr
28. GermanÄther
29. GermanEther
30. Ancient Greekῡ̔́λη (hū́lē)
31. GermanEthy
32. Englishethyl
33. English todayhydroxyethyl

From hydroxy- + ethyl.