The name "Erewash" is pronounced ɛrɛwɔʃ. Its approximate meaning is not in doubt, but there is room for debate about the precise derivation and its connotations. Brewer gives the commonly accepted explanation that it comes from the Old English words irre ("wandering") and wisce ("wet meadow"). This is accepted by Cameron, a leading place name expert, and a Derbyshire specialist, who interprets the name as "wandering, marshy river". Gelling, who specialises in seeking precise topgraphical equivalents for toponymic elements, confirms that wisce signifies a marshy meadow but gives only southern examples. She conjectures that there is an element, wæsse, perhaps Old English, that signifies very specifically "land by a meandering river which floods and drains quickly", and her examples are primarily Midland and northern. This seems to fit the Erewash perfectly. A good example of the meandering character of the river will be seen around Gallows Inn Playing Fields, Ilkeston, where rapid flooding and draining occur frequently.
The Erewash rises in Kirkby-in-Ashfield, Nottinghamshire, but is partly culverted as it flows south westward from the town. It surfaces definitively to the north of Kirkby Woodhouse and flows roughly westward, under the M1 motorway, and between Pinxton and Selston. It then becomes the approximate county border between Nottinghamshire and Derbyshire, flowing roughly south, between Langley Mill and Eastwood, skirting the east of Ilkeston. The river continues south between Sandiacre and Stapleford until, at Toton, it turns east and flows into the River Trent, at the Attenborough Nature Reserve, near Long Eaton.
The river gives its name to the Erewash Valley, which has a rich industrial history (and a local council too).
Although the river is not navigable at any part, it is paralleled by the Erewash Canal for much of its length, from (Langley Mill to the River Trent); north of Langley Mill, it was paralleled by the abandoned Cromford Canal (from the branch to Pinxton).
For such a small river, the Erewash has a surprisingly high literary profile, due almost entirely to D H Lawrence, who mentions it several times, and centres a number of works in the Erewash valley. A reference at the beginning of The Rainbow is perhaps the most telling from the geographical point of view:
- "The Brangwens had lived for generations on the Marsh Farm, in the meadows where the Erewash twisted sluggishly through alder trees, separating Derbyshire from Nottinghamshire."
- John Ayto and Ian Crofton, Brewer's Britain and Ireland, London: Weidenfeld and Nicolson, 2005, ISBN 0-304-35385-X, p.399.
- Kenneth Cameron, English Place Names, London: Batsford, 1996, ISBN 0-7134-7378-9, p.169
- Margaret Gelling, Place-Names in the Landscape, London: J.M. dent, 1984, ISBN 0-460-86086-0, p.250
- Margaret Gelling, Place-Names in the Landscape, London: J.M. dent, 1984, ISBN 0-460-86086-0, p.59