tetraiodide

The story

1. Proto-Indo-European*kʷetwóres
2. Proto-Hellenic*kʷétwores
3. Ancient Greekτέσσᾰρες (téssăres)
4. Ancient Greekτετρᾰ- (tetră-)
5. Englishtetra-
6. Proto-Hellenic*wion
7. Ancient Greekῐ̓́ον (ĭ́on)
8. Proto-Indo-European*h₃ed-
9. Proto-Indo-European*h₃édyeti
10. Proto-Hellenic*ód͏̌d͏̌ō
11. Ancient Greekὄζω (ózō)
12. Ancient Greekῐ̓ώδης (ĭṓdēs)
13. Frenchiode
14. Englishiodine
15. Proto-Indo-European*dʰeh₁-
16. Englishiodide
17. English todaytetraiodide

From tetra- + iodide.