behavioral

The story

1. Proto-Indo-European*h₁ep-
2. Proto-Indo-European*h₁éps
3. Proto-Indo-European*h₁épi
4. Proto-Indo-European*h₁pi
5. Proto-Germanic*bi
6. Proto-Germanic*bi-
7. Proto-West Germanic*bi-
8. Proto-Indo-European*kap-
9. Proto-Germanic*habjaną
10. Proto-West Germanic*habbjan
11. Proto-West Germanic*bihabbjan
12. Old Englishbehabban
13. Middle Englishbehaven
14. Proto-Indo-European*gʰeh₁bʰ-
15. Proto-Indo-European*gʰh₁bʰéh₁yeti
16. Proto-Italic*haβēō
17. Latinhabeō
18. Old Frenchavoir
19. Middle Englishhavour
20. Middle Englishbehavoure
21. Englishbehavior
22. Proto-Indo-European*h₂el-
23. Proto-Indo-European*h₂élisder.?
24. English todaybehavioral

From behavior + -al.