The entry into the English language of the informal usage of schizophrenia as split personality/Jekyll and Hyde is traced and commented upon. The metaphor of split personality is followed from Eugene Bleuler via his translators and the wider psychiatric community into the present day. It, and to a lesser extent the Jekyll-Hyde personality, is found to be as much a product of the psychological professions as a product of lay misinterpretation. The informal definition of schizophrenia as split personality has outlived the scientific theory with which it was initially associated.