subchairman

The story

1. Proto-Indo-European*upó
2. Proto-Italic*supo
3. Latinsub
4. Latinsub-
5. Englishsub-
6. Proto-Indo-European*ḱe?
7. Proto-Indo-European*ḱóm
8. Proto-Indo-European*ḱm̥-th₂der.?
9. Proto-Hellenic*kətá
10. Ancient Greekκατά (katá)
11. Proto-Indo-European*sed-
12. Proto-Indo-European*sedreh₂
13. Proto-Hellenic*hédrā
14. Ancient Greekἕδρα (hédra)
15. Ancient Greekκᾰθέδρᾱ (kăthédrā)
16. Latincathedra
17. Old Frenchchaiere
18. Middle Englishchayere
19. Englishchair
20. Proto-Indo-European*mon-
21. Proto-Germanic*mann-
22. Proto-West Germanic*mann
23. Old Englishmann
24. Middle Englishman
25. Englishchairman
26. English todaysubchairman

From sub- + chairman.