The word 'therapy' entered English in the mid-19th century, borrowed directly from Modern Latin 'therapia', which itself came from the Greek 'therapeia' meaning "curing, healing, service done to the sick". This Greek noun is derived from the verb 'therapeuein', meaning "to attend, do service, take care of, treat medically". The core concept of attentive, caring service evolved specifically into the medical sense of treatment. The term reflects a holistic historical view of healing as an act of devoted service and attendance upon a patient.

The word is a simplex loanword from Greek. It is not productively segmented into meaningful substrings in modern English spelling.