polyester

The story

1. Proto-Indo-European*pleh₁-
2. Proto-Indo-European*polh₁ús
3. Ancient Greekπολῠ́ς (polŭ́s)
4. Englishpoly-
5. Proto-Indo-European*h₂eḱ-
6. Proto-Indo-European*h₂eḱéh₁yeti
7. Proto-Italic*akēō
8. Latinaceō
9. Latinacēscō
10. Latinacētum
11. Proto-West Germanic*aket
12. Proto-West Germanic*atek
13. Old High Germaneȥȥih
14. Middle High Germaneȥȥich
15. GermanEssich
16. GermanEssig
17. Proto-Indo-European*h₂eydʰ-
18. Proto-Hellenic*áitʰō
19. Ancient Greekαἴθω (aíthō)
20. Ancient Greekᾱ̓ήρ (āḗr)influ.?
21. Ancient Greekαἰθήρ (aithḗr)
22. Latinaethēr
23. GermanÄther
24. GermanEster
25. Englishester
26. English todaypolyester

From poly- + ester.