thyrotoxic

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. Ancient Greekτόξον (tóxon)
14. Ancient Greekτοξῐκός (toxĭkós)
15. Ancient Greekτοξικόν (toxikón)
16. Latintoxicum
17. Latintoxicu
18. Frenchtoxique
19. Englishtoxic
20. English todaythyrotoxic

From thyro- + toxic.