buserelin

The story

1. Proto-Indo-European*tréyes
2. Proto-Indo-European*tri-
3. Proto-Indo-European*tritós
4. Proto-Italic*tritios
5. Latintertius
6. Englishtert-
7. Proto-Indo-European*gʷṓws
8. Proto-Hellenic*gʷous
9. Ancient Greekβοῦς (boûs)
10. Proto-Indo-European*tewh₂-
11. Proto-Indo-European*tuh₂rós
12. Proto-Hellenic*tūrós
13. Ancient Greekτῡρός (tūrós)
14. Ancient Greekβούτῡρος (boútūros)
15. Englishbut-
16. Proto-Indo-European*swel-der.?
17. Ancient Greekῡ̔́λη (hū́lē)
18. Englishbutyl
19. Englishtert-butyl
20. Old Chinese絲 (*sə)der.?
21. Ancient Greekσήρ (sḗr)
22. Ancient Greekσηρῐκός (sērĭkós)
23. Latinsēricus
24. Englishserine
25. Proto-Italic*wre-
26. Latinre-
27. Old Frenchre-
28. Proto-Indo-European*(s)leg-
29. Proto-Indo-European*(s)leg-s-ós
30. Latinlaxus
31. Latinlaxō
32. Vulgar Latin*laxicāre
33. Vulgar Latin*lassicāre
34. Old Frenchlaschier
35. Old Frenchrelaschier
36. Old Frenchrelaisser
37. Middle Englishrelesen
38. Englishrelease
39. English todaybuserelin

From (tert-)bu(tyl) + se(rine) + -relin (“LHRH release–stimulating peptide”).