Water was of major importance to the early settlers of an area, both for subsistence and for religious reasons. Names were given to springs, streams, rivers and lakes as well as marshes, bays and seas. Eilert Ekwall carried out an early study of river names in England while Krahe conducted a European-wide examination of river names which showed that there were common roots in the names over a wide area. There is still controversy over the language of these roots. Sometimes a generic word was adopted as a specific label, for example the Celtic word for river was "afon" which is used in many cases as the name (Avon) of rivers in England.