A transposed variant spelling which derives from the Norse-Viking 'dembel' meaning a clear pool or stream and 'byr' - meaning a farmstead. In this case we have an apparently intrusive 'low' which does not appear in Norse and is caused by dialectual change. With locational names, in this case from Dembelby a village in Lincolnshire, corruption occurs through distance, the futher the original name holder moved, usually the greater the corruptive influence and the more so if the original spelling was 'foreign'. The first recorded spelling of the family name is shown to be that of Eustace de Denbelby which was dated C. 1190 The Pipe Rolls of Lincoln during the reign of King Richard 1 The Lionheart 1189-1199 Surnames became necessary when governments introduced personal taxation. In England this was known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.