diphenylcyanoarsine

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*bʰeh₂-
8. Proto-Indo-European*bʰh₂nyéti
9. Proto-Hellenic*pʰáňňō
10. Ancient Greekφαίνω (phaínō)
11. Frenchphéno-
12. Proto-Indo-European*swel-der.?
13. Ancient Greekῡ̔́λη (hū́lē)
14. Frenchphényle
15. Englishphenyl
16. Englishdiphenyl
17. Proto-Indo-European*ḱwey-
18. Proto-Hellenic*kúwanos
19. Ancient Greekκῠ́ᾰνος (kŭ́ănos)
20. Ancient Greekκῠᾰ́νεος (kŭắneos)
21. Englishcyano-
22. Proto-Indo-European*ǵʰelh₃-
23. Proto-Indo-European*ǵʰl̥h₃enyom
24. Proto-Indo-Iranian*ȷ́ʰr̥Hanyam
25. Proto-Iranian*jr̥Hanyam
26. Old Median*zaranyam
27. Old Median*kā
28. Old Median*zaraniyakā
29. Middle Persian*zarnīk
30. Classical Syriacܙܪܢܝܟܐ (zarnīḵā)
31. Arabicالزَرْنِيخ (az-zarnīḵ)
32. Medieval Greekἀρσενικόν (arsenikón)
33. Latinarsenicum
34. Middle Frencharsenic
35. Middle Englisharsenik
36. Englisharsenic
37. Englisharsine
38. English todaydiphenylcyanoarsine

From diphenyl + cyano- + arsine.