1950s; earliest use found in Journal of Hygiene. From the name of the Royal FreeHospital in London, where a cluster of cases occurred in 1955 + disease.
Definition of Royal Free disease in US English:
Royal Free disease
nounˌrɔɪəl ˈfriː dɪˌziːz
Chronic fatigue syndrome.
Origin
1950s; earliest use found in Journal of Hygiene. From the name of the Royal FreeHospital in London, where a cluster of cases occurred in 1955 + disease.