dipotassium

The story

1. Proto-Indo-European*dwóh₁
2. Proto-Indo-European*dwi-
3. Proto-Hellenic*dwi-
4. Ancient Greekδῐ- (dĭ-)
5. Latindi-
6. Englishdi-
7. Proto-Germanic*puttaz
8. Frankish*pott
9. Old Dutch*pot
10. Middle Dutchpot
11. Dutchpot
12. Proto-Indo-European*h₂eHs-der.?
13. Proto-Germanic*askǭ
14. Proto-West Germanic*askā
15. Old Dutch*aska
16. Middle Dutchasche
17. Dutchas
18. Dutchpotas
19. Dutchpotasch
20. Englishpotassa
21. Englishpotassium
22. English todaydipotassium

From di- + potassium.