From ergo- +‎ therapy.

ergotherapy (uncountable)

1. Work as a form of occupational therapy.
   • 2003, Paula Kramer, Perspectives in Human Occupation: Participation in Life, page 24:

     As a physician, Dunton understood the importance of being seen as scientifically valid, thus his support for ergotherapy, a term that he believed would be more impressive to the scientific community.