reactivate

The story

1. Proto-Italic*wre-
2. Latinre-
3. Old Frenchre-
4. Middle Englishre-
5. Englishre-
6. Proto-Indo-European*h₂eǵ-
7. Proto-Indo-European*h₂éǵeti
8. Proto-Italic*agō
9. Latinagō
10. Ancient Greekἐνεργητικός (energētikós)
11. Latināctīvu
12. Old Frenchactif
13. Middle Englishactyf
14. Englishactive
15. Englishactivate
16. English todayreactivate

From re- + activate.