acetylchitooligosaccharide

The story

1. Proto-Indo-European*h₂eḱ-
2. Proto-Indo-European*h₂eḱéh₁yeti
3. Proto-Italic*akēō
4. Latinaceō
5. Latinacēscō
6. Latinacētum
7. Englishaceto-
8. Englishacet-
9. Proto-Indo-European*swel-der.?
10. Ancient Greekῡ̔́λη (hū́lē)
11. Englishacetyl
12. Ancient Greekχῐτών (khĭtṓn)
13. Latinchitōn
14. Frenchchitine
15. Englishchitin
16. Englishchito-
17. Ancient Greekὀλῐ́γος (olĭ́gos)
18. Englisholigo-
19. Proto-Indo-European*ḱorkeh₂
20. Proto-Indo-Iranian*ćárkaraH
21. Proto-Indo-Aryan*śárkaraH
22. Sanskritशर्क॑रा (śárkarā)
23. Palisakkharā
24. Ancient Greekσάκχαρ (sákkhar)
25. Latinsaccharon
26. Latinsaccharum
27. Englishsaccharo-
28. Proto-Indo-European*dʰeh₁-
29. Englishsaccharide
30. Englisholigosaccharide
31. Englishchitooligosaccharide
32. English todayacetylchitooligosaccharide

From acetyl + chitooligosaccharide.