dimethylarsinate

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-Indo-European*médʰu
8. Proto-Hellenic*métʰu
9. Ancient Greekμέθυ (méthu)
10. Proto-Indo-European*swel-der.?
11. Ancient Greekῡ̔́λη (hū́lē)
12. GermanMethy
13. Englishmethyl
14. Englishmethyl-
15. Proto-Indo-European*ǵʰelh₃-
16. Proto-Indo-European*ǵʰl̥h₃enyom
17. Proto-Indo-Iranian*ȷ́ʰr̥Hanyam
18. Proto-Iranian*jr̥Hanyam
19. Old Median*zaranyam
20. Old Median*kā
21. Old Median*zaraniyakā
22. Middle Persian*zarnīk
23. Classical Syriacܙܪܢܝܟܐ (zarnīḵā)
24. Arabicالزَرْنِيخ (az-zarnīḵ)
25. Medieval Greekἀρσενικόν (arsenikón)
26. Latinarsenicum
27. Middle Frencharsenic
28. Middle Englisharsenik
29. Englisharsenic
30. Englisharsine
31. Englisharsinate
32. English todaydimethylarsinate

From di- + methyl- + arsinate.