psychotherapist

The story

1. Ancient Greekψῡχή (psūkhḗ)
2. Ancient Greekψῡχο- (psūkho-)
3. Englishpsycho-
4. Proto-Indo-European*treb-der.?
5. Ancient Greekθερᾰ́πων (therắpōn)
6. Ancient Greekθεραπεύω (therapeúō)
7. Ancient Greekθεραπεία (therapeía)
8. New Latintherapīa
9. Englishtherapy
10. Englishtherapist
11. Englishpsycho-
12. Englishtherapy
13. Englishpsychotherapy
14. English todaypsychotherapist

From psycho- + therapist, or from psychotherapy + -ist.