parathyroid

The story

1. Proto-Indo-European*per-
2. Proto-Indo-European*preh₂-
3. Proto-Hellenic*pərai
4. Ancient Greekπᾰρᾰ́ (părắ)
5. Ancient Greekπᾰρᾰ- (pără-)
6. Englishpara-
7. Proto-Indo-European*dʰwer-
8. Proto-Hellenic*tʰurā
9. Ancient Greekθῠ́ρᾱ (thŭ́rā)
10. Ancient Greekθῠρεός (thŭreós)
11. Proto-Indo-European*weyd-
12. Proto-Indo-European*wéydos
13. Proto-Hellenic*wéidos
14. Ancient Greekεἶδος (eîdos)
15. Ancient Greekθῠρεοειδής (thŭreoeidḗs)
16. New Latinthyreoīdēs
17. Englishthyroid
18. English todayparathyroid

From para- + thyroid.