craniosurgical

The story

1. Proto-Indo-European*ḱer-
2. Proto-Indo-European*ḱerh₂-
3. Proto-Indo-European*ḱérh₂sō
4. Proto-Hellenic*kárahə
5. Ancient Greek*κρᾱν- (*krān-)
6. Ancient Greekκρᾱνῐ́ον (krānĭ́on)
7. Medieval Latincrānium
8. Englishcranio-
9. Proto-Indo-European*ǵʰes-
10. Proto-Indo-European*ǵʰésōr
11. Proto-Hellenic*kʰéhər
12. Ancient Greekχείρ (kheír)
13. Proto-Indo-European*werǵ-
14. Proto-Indo-European*worǵós
15. Proto-Hellenic*worgós
16. Ancient Greekχειρουργός (kheirourgós)
17. Ancient Greekχειρουργῐκός (kheirourgĭkós)
18. Late Latinchīrurgicus
19. Proto-Indo-European*h₂el-
20. Proto-Indo-European*h₂élisder.?
21. Medieval Latincirurgicālis
22. Middle Frenchcirurgica
23. Middle Englishcirurgical
24. Englishsurgical
25. English todaycraniosurgical

From cranio- + surgical.