Great Ouse

The River Great Ouse ( OOZ) is a river in England, the fifth longest in the United Kingdom, and longest of several British rivers called "Ouse". It flows mostly north and east, from Syresham in Northamptonshire, through Buckinghamshire, Bedfordshire, Cambridgeshire and Norfolk, before draining into the Wash and the North Sea near Kings Lynn. Authorities disagree both on the river's source and its length, with one quoting 160 mi (260 km)
and another 143 mi (230 km). The Great Ouse has been historically important for commercial navigation, and for draining the low-lying region through which it flows; its best-known tributary is the Cam, which runs through Cambridge. Its lower course passes through drained wetlands and fens and has been extensively modified, or channelised, to relieve flooding, stabilise its path, and provide a better route for barge traffic.
The name Ouse is from the Celtic or pre-Celtic *Udso-s, and probably means simply "water" or slow flowing river. The lower reaches of the Great Ouse are also known as "Old West River" and "the Ely Ouse", but the entire length of the river is often referred to simply as the Ouse in informal usage (the word "Great" – which originally meant simply big or, in the case of a river, long – is used to distinguish this river from several others called the Ouse).

Source: Wikipedia https://en.wikipedia.org/wiki/River_Great_Ouse