hydroxide

The story

1. Proto-Indo-European*wed-
2. Proto-Indo-European*wódr̥
3. Proto-Hellenic*údōr
4. Ancient Greekῡ̆̔́δωρ (hū̆́dōr)
5. Ancient Greekῠ̔δρο- (hŭdro-)
6. Englishhydro-
7. Proto-Indo-European*h₂eḱ-der.?
8. Ancient Greekὀξύς (oxús)
9. Proto-Indo-European*ǵenh₁-
10. Proto-Indo-European*ǵénh₁os
11. Proto-Hellenic*génos
12. Ancient Greekγένος (génos)
13. Frenchoxygène
14. Proto-Indo-European*h₂eḱ-
15. Proto-Indo-European*h₂eḱéh₁yeti
16. Proto-Italic*akēō
17. Latinaceō
18. Proto-Indo-European*dʰeh₁-
19. Latinacidu
20. Frenchacide
21. Frenchoxide
22. Englishoxide
23. English todayhydroxide

From hydro- + oxide.