postreactivation

The story

1. Proto-Indo-European*pós
2. Proto-Indo-European*pósti
3. Proto-Italic*posti
4. Old Latinposte
5. Latinpost
6. Englishpost-
7. Proto-Italic*wre-
8. Latinre-
9. Old Frenchre-
10. Middle Englishre-
11. Englishre-
12. Proto-Indo-European*h₂eǵ-
13. Proto-Indo-European*h₂éǵeti
14. Proto-Italic*agō
15. Latinagō
16. Ancient Greekἐνεργητικός (energētikós)
17. Latināctīvu
18. Old Frenchactif
19. Middle Englishactyf
20. Englishactive
21. Englishactivate
22. Englishactivation
23. Englishreactivation
24. English todaypostreactivation

From post- + reactivation.