overpants

The story

1. Proto-Indo-European*úp
2. Proto-Indo-European*upér
3. Proto-Germanic*uber
4. Old Englishofer-
5. Middle Englishover-
6. Englishover-
7. Proto-Indo-European*peh₂-
8. Proto-Indo-European*ph₂énts?
9. Proto-Hellenic*pánts
10. Ancient Greekπᾶς (pâs)
11. Ancient Greekἐλεήμων (eleḗmōn)
12. Ancient GreekΠαντελεήμων (Panteleḗmōn)
13. ItalianPantalone
14. Frenchpantalon
15. Englishpantaloon
16. Englishpantaloons
17. Englishpants
18. English todayoverpants

From over- + pants.