Quartan ague A fever which reoccurred every fourth day; one of the indeterminate febrile ailments of the period, sweating sickness, probably influenza, which could be fatal. Lat. quartanus = of the fourth] (From Dictionary of Medieval Terms and Phrases) Referring entries Saturday 1 September 1638 Leave a Reply Cancel replyYour email address will not be published. Required fields are marked *Comment Name * Email * Website Notify me of new posts by email. This site uses Akismet to reduce spam. Learn how your comment data is processed.