This is a good example of transposition of spelling through distance and dialect. The origination is from the Olde English pre 10th Century 'Tre-Win' meaning 'Wyns Homestead' and found in the modern Cornish 'Trewyn'. The name travelled back into England from Cornwall and developed dialectually as Treen or Treend, as well as Trewin, and even Trees and possibly Train, the latter also having a further locational meaning of 'One resident in the Trees'. The first recorded spelling of the family name is shown to be that of Thomas atte Trewen. which was dated 1311, The Name Register of Devon. during the reign of King Edward II, Edward of Caernafon, 1307 - 1327. 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.