interpolar

The story

1. Proto-Indo-European*h₁én
2. Proto-Indo-European*h₁n̥tér
3. Proto-Italic*n̥ter
4. Latininter
5. Latininter-
6. Englishinter-
7. Proto-Indo-European*kʷel-
8. Proto-Indo-European*kʷól-os
9. Proto-Hellenic*pólos
10. Ancient Greekπόλος (pólos)
11. Latinpolus
12. Proto-Indo-European*h₂el-
13. Proto-Indo-European*h₂élisder.?
14. Late Latinpolāri
15. Englishpolar
16. English todayinterpolar

From inter- + polar.