rheumatism

First recorded in 1601, rheumatism comes from Latin rheumatismus ("rheum"), which was borrowed from Ancient Greek ῥευματισμός (rheumatismós), meaning "humour, discharge, rheum."

The Greek noun traces back to the verb ῥευματίζομαι ("to suffer from a rheum"), itself built on ῥεῦμα ("stream, flow") and ultimately the verb ῥέω ("to flow") — so a condition of stiff, painful joints was once understood through the image of bodily fluids flowing where they shouldn't.

It shares its root ῥέω ("to flow") with the Greek-derived word rheum, the discharge or mucus the ancients believed caused the condition.