A Cornish locational name which originates in the village of Constantine, on the edge of the Helford River Estuary. The name derives from the Cornish 'tre' meaning 'homestead' and the personal name of the pre 8th Century 'Dewin' - meaning 'a wizard or magician' and also more popularily recorded as 'Merlin'. In addition to the first recording, the name appears as Trethouen in 1327 in the first year of the reign of Edward 111. The first recorded spelling of the family name is shown to be that of Robertus Tredewen. which was dated 1195, The Accounts of the Duchy of Cornwall. 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.