hexaoxide

The story

1. Proto-Indo-European*swéḱs
2. Proto-Hellenic*hwéks
3. Ancient Greekἕξ (héx)
4. Ancient Greekἑξα- (hexa-)
5. Latinhexa-
6. Englishhexa-
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. Latinacidu
15. Frenchacide
16. Frenchoxide
17. Englishoxide
18. English todayhexaoxide

From hexa- + oxide.