unactive

The story

1. Proto-Indo-European*né
2. Proto-Indo-European*n̥-
3. Proto-Germanic*un-
4. Proto-West Germanic*un-
5. Old Englishun-
6. Middle Englishun-
7. Englishun-
8. Proto-Indo-European*h₂eǵ-
9. Proto-Indo-European*h₂éǵeti
10. Proto-Italic*agō
11. Latinagō
12. Ancient Greekἐνεργητικός (energētikós)
13. Latināctīvu
14. Old Frenchactif
15. Middle Englishactyf
16. Englishactive
17. English todayunactive

From un- + active. Piecewise doublet of inactive.