Rhea sister
/ˈriːə ˌsɪstə/(also Rea sister, Ria sister) humorous
noun
In plural Diseases ending in -rhoea or -rhea, as diarrhoea, gonorrhoea, pyorrhoea, etc., personified.
Origin
1930s. From -rhea + sister, with -rhea treated humorously as a surname.