psychodiagnostically

The story

1. Ancient Greekψῡχή (psūkhḗ)
2. Ancient Greekψῡχο- (psūkho-)
3. Englishpsycho-
4. Proto-Indo-European*dwóh₁
5. Proto-Indo-European*trísinflu.
6. Proto-Indo-European*dwís
7. Ancient Greekδιά (diá)
8. Ancient Greekδια- (dia-)
9. Proto-Indo-European*ǵneh₃-
10. Proto-Indo-European*ǵn̥h₃sḱéti
11. Proto-Hellenic*gignṓskō
12. Ancient Greekγῐγνώσκω (gĭgnṓskō)
13. Ancient Greekδῐαγῐγνώσκω (dĭagĭgnṓskō)
14. Ancient Greekδῐᾰ́γνωσῐς (dĭắgnōsĭs)
15. Ancient Greekδῐᾰ- (dĭă-)
16. Proto-Indo-European*ǵneh₃-
17. Proto-Indo-European*ǵneh₃tis
18. Ancient Greekγνῶσις (gnôsis)
19. Ancient Greekγνωστῐκός (gnōstĭkós)
20. Ancient Greekδῐαγνωστῐκός (dĭagnōstĭkós)
21. Englishdiagnostic
22. Englishpsychodiagnostic
23. Proto-Indo-European*h₂el-
24. Proto-Indo-European*h₂élisder.?
25. Proto-Indo-European*leyg-
26. Proto-Germanic*līką
27. English todaypsychodiagnostically

From psychodiagnostic + -ally. By surface analysis, psycho- + diagnostically.