This is a locational surname which almost always originates from the town of Castleton, in the county of Derbyshire, England. There are villages called by the same name in both Lancashire and Yorkshire, but in general it is the Derbyshire 'Casleton' which has provided the surname. The spelling forms are most unusual in that the name is equally popular in certain parts of Derbyshire as both Castleton and Castledine, whilst in the London registers from the middle of the 16th century the spelling forms include Caselden, Castletine, and Casteldon. The 'Castledine' spelling seems to derive from a local dialectal pronunciation of the Middle Ages, when the letters 'd' and 't' were interchangeable. The town is first recorded in the famous Domesday Book of the year 1086 as 'Castellum Willelmi peuerel', or 'the castle of young William'. This latter person was the youngest (natural) son of William, The Conqueror, and he was granted lands in various parts of England. It seems however that within a fairly short time the place name was abbreviated to its (near) present form in the 13th century, where it is recorded in the charters of Derbyshire as 'Castelton', or 'the place (tun) by the castle'. Early examples of the surname recordings taken from the church registers include Alice Castleton, christened at the church of St Benet Fink, London, on February 23rd 1564, and Bendicta Caselden, christened at St Mary Abchurch, London, on June 27th 1621. In Derbyshire the epri-centre of the name seems to have been the village of Wilne, near Draycott in the Clay. One of the earliest recordings from the area being Elizabeth Castledine, christened there on February 19th 1680. The first recorded spelling of the family name is shown to be that of Sir Richard de Castillton, which was dated 1298, in the roll of the 'battell of Falkirk', Scotland, during the reign of King Edward 1st, known as 'The hammer of the Scots', 1272 - 1307. 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.