The term "Ague spleen" is an archaic medical term referring to the swelling of the spleen associated with malaria. The word "ague" is pronounced /ˈeɪɡjuː/, while "spleen" is pronounced /spli:n/. The spelling of the word can be explained by the origin of the term in the Middle Ages, where "ague" was used to describe any illness that caused fever and chills. The term "spleen" was added to describe the specific symptom associated with malaria. The spelling has remained consistent despite the obsolescence of the term.