"morbid frequent evacuation of the bowels," late 14c., diaria, from Old French diarrie, from Late Latin diarrhoea, from Greek diarrhoia "diarrhea" (coined by Hippocrates), literally "a flowing through," from diarrhein "to flow through," from dia- "through" (see dia-) + rhein "to flow" (from PIE root *sreu- "to flow"). Respelled 16c. from diarria on Latin model.