The story
Coined in a 2003 paper by Gerald Rosen and Gerald Davison, from the idea of wearing a purple hat in addition to other treatment.
Etymology from Wiktionary, CC BY-SA 4.0.
purple hat therapy
Today it means: Any medical practice in which an established form of therapy is combined with an unlikely new addition and is then claimed to be effective because of the new addition, when in fact the effectiveness is due to the established component. Full definition →