The name Churn is ancient, certainly pre-Roman, and probably has its origins in the Celtic language spoken by the Dobunni tribe who controlled the area before the Roman conquest in the 1st Century CE. The original name may have sounded similar to Korinn.
Cognate names and name elements from the area are Cerney, Ciren and Corin as found in the villages of North Cerney, South Cerney, and Cerney Wick, modern Cirencester, and the Roman town name Corinium. All these places are on or close to the River Churn.