coadapt

The story

1. Proto-Indo-European*ḱe?
2. Proto-Indo-European*ḱóm
3. Proto-Italic*kom
4. Proto-Italic*kom-
5. Latincon-
6. Latinco-
7. Englishco-
8. Proto-Indo-European*h₂éd
9. Proto-Italic*ad
10. Proto-Italic*ad-
11. Latinad-
12. Proto-Indo-European*h₂ep-
13. Proto-Indo-European*h₂ptós
14. Proto-Italic*aptos
15. Latinaptus
16. Proto-Indo-European[Term?]
17. Proto-Italic*apjō
18. Latinapiō
19. Latinaptō
20. Latinadaptō
21. Middle English*adapten
22. Englishadapt
23. English todaycoadapt

From co- + adapt.