The origin of the name is unknown. There is one theory that the Frays River began when a tree falling across the Colne deflected a branch of the river away from its natural and persistent channel. What seems more likely is that it is a man-made diversion of the River Colne created to power mills in the Uxbridge area. It is also sometimes known as the Uxbridge and Cowley Mill Stream, the Cowley Stream or Colham Mill Stream.
The road from London to Oxford is a very ancient and important route. The town of Uxbridge grew up as a daughter settlement of the village of Hillingdon, along the road where it crossed the River Colne. Uxbridge is not mentioned by name in the Domesday survey of 1086; it is probably included with the entries for Hillingdon and Colham.