polariscope

The story

1. Proto-Indo-European*kʷel-
2. Proto-Indo-European*kʷól-os
3. Proto-Hellenic*pólos
4. Ancient Greekπόλος (pólos)
5. Latinpolus
6. Proto-Indo-European*h₂el-
7. Proto-Indo-European*h₂élisder.?
8. Late Latinpolāri
9. Englishpolar
10. Proto-Indo-European*speḱ-
11. Proto-Indo-European*spéḱyeti
12. Proto-Hellenic*sképt͏̌omai
13. Ancient Greekσκέπτομαι (sképtomai)
14. Ancient Greekσκοπός (skopós)
15. Ancient Greekσκοπέω (skopéō)
16. English todaypolariscope

From polar + -scope.