polyoxoanion

The story

1. Proto-Indo-European*pleh₁-
2. Proto-Indo-European*polh₁ús
3. Ancient Greekπολῠ́ς (polŭ́s)
4. Englishpoly-
5. Proto-Indo-European*h₂eḱ-der.?
6. Ancient Greekὀξύς (oxús)
7. Proto-Indo-European*ǵenh₁-
8. Proto-Indo-European*ǵénh₁os
9. Proto-Hellenic*génos
10. Ancient Greekγένος (génos)
11. Frenchoxygène
12. Englishoxygen
13. Englishoxo-
14. Proto-Indo-European*h₂en-
15. Proto-Hellenic*aná
16. Ancient Greekᾰ̓νᾰ́ (ănắ)
17. Ancient Greekᾰ̓νᾰ- (ănă-)
18. Proto-Indo-European*h₁ey-
19. Proto-Indo-European*h₁éyti
20. Proto-Hellenic*éimi
21. Ancient Greekῐ̓όν (ĭón)
22. Ancient Greekἀνῐόν (anĭón)
23. Englishanion
24. Englishoxoanion
25. English todaypolyoxoanion

From poly- + oxoanion.