carboxy

The story

1. Proto-Indo-European*kerh₃-der.?
2. Latincarbōnem
3. Frenchcarbone
4. Englishcarbon
5. Proto-Indo-European*swel-der.?
6. Ancient Greekῡ̔́λη (hū́lē)
7. Englishcarbonyl
8. Proto-Indo-European*wed-
9. Proto-Indo-European*wódr̥
10. Proto-Hellenic*údōr
11. Ancient Greekῡ̆̔́δωρ (hū̆́dōr)
12. Ancient Greekὑδρο- (hudro-)
13. Frenchhydro-
14. Proto-Indo-European*ǵenh₁-
15. Proto-Indo-European*ǵénh₁os
16. Proto-Hellenic*génos
17. Ancient Greekγένος (génos)
18. Frenchhydrogène
19. Englishhydrogen
20. Proto-Indo-European*h₂eḱ-der.?
21. Ancient Greekὀξύς (oxús)
22. Ancient Greekγένος (génos)
23. Frenchoxygène
24. Englishoxygen
25. Englishhydroxyl
26. Englishcarboxyl
27. English todaycarboxy

From carboxyl.