Late Middle English (in an earlier sense). From post-classical Latin rheumatizare to suffer from rheum or catarrh, to flow as rheum, to fill with rheum or its etymon Hellenistic Greek ῥευματίζειν (more commonly ῥευματίζεσθαι, passive) from ῥευματ-, ῥεῦμα + -ίζειν. In later use perhaps independently from rheumat- + -ize. Compare Middle French reumatiser, reumatizer to cause rheumatism, to cause (someone) to suffer from rheumatism, French rhumatiser, and also Middle French reumatizant, French rheumatisant that causes rheumatism.