cyclopolyarsine

The story

1. Proto-Indo-European*kʷelh₁-redup.
2. Proto-Indo-European*kʷékʷlos
3. Proto-Hellenic*kʷókʷlos
4. Proto-Hellenic*kúklos
5. Ancient Greekκύκλος (kúklos)
6. Late Latincyclus
7. Middle Englishcicle
8. Englishcycle
9. Ancient Greekκύκλος (kúklos)
10. Ancient Greekκυκλῐκός (kuklĭkós)
11. Classical Latincyclicu
12. Middle Frenchcyclique
13. Frenchcyclique
14. Classical Latincyclicus
15. Englishcyclic
16. Englishcyclo-
17. Proto-Indo-European*pleh₁-
18. Proto-Indo-European*polh₁ús
19. Ancient Greekπολῠ́ς (polŭ́s)
20. Englishpoly-
21. Proto-Indo-European*ǵʰelh₃-
22. Proto-Indo-European*ǵʰl̥h₃enyom
23. Proto-Indo-Iranian*ȷ́ʰr̥Hanyam
24. Proto-Iranian*jr̥Hanyam
25. Old Median*zaranyam
26. Old Median*kā
27. Old Median*zaraniyakā
28. Middle Persian*zarnīk
29. Classical Syriacܙܪܢܝܟܐ (zarnīḵā)
30. Arabicالزَرْنِيخ (az-zarnīḵ)
31. Medieval Greekἀρσενικόν (arsenikón)
32. Latinarsenicum
33. Middle Frencharsenic
34. Middle Englisharsenik
35. Englisharsenic
36. Englisharsine
37. English todaycyclopolyarsine

From cyclo- + poly- + arsine.