thyrofissure

The story

1. Proto-Indo-European*dʰwer-
2. Proto-Hellenic*tʰurā
3. Ancient Greekθῠ́ρᾱ (thŭ́rā)
4. Ancient Greekθῠρεός (thŭreós)
5. Proto-Indo-European*weyd-
6. Proto-Indo-European*wéydos
7. Proto-Hellenic*wéidos
8. Ancient Greekεἶδος (eîdos)
9. Ancient Greekθῠρεοειδής (thŭreoeidḗs)
10. New Latinthyreoīdēs
11. Englishthyroid
12. Englishthyro-
13. Proto-Indo-European*bʰeyd-
14. Proto-Indo-European*bʰinédti
15. Proto-Italic*findō
16. Latinfindō
17. Latinfissūra
18. Old Frenchfissure
19. Middle Englishfissure
20. Englishfissure
21. English todaythyrofissure

From thyro- + fissure.