This interesting surname is of Anglo-Saxon origin, and is a locational name from a number of places thus called, for example Underdown, south-east of Ludbury in Herefordshire; Underdown, south of Chartham in Kent; and Underdown, south of Herne Bay in Kent. The derivation of the placename is from the Olde English pre 7th Century "under", under, below, and "dun", down, hill, mountain; hence, "under the hill", or "at the foot of the hill". During the Middle Ages, when migration for the purpose of job-seeking was becoming more common, people often took their former village name as a means of identification, thus resulting in a wide dispersal of the name. In some instances the surname may be topographical for a "dweller at the foot of the hill". Theobald de Underdoune is listed in the 1316 Feet of Fines of Kent. In the modern idiom the surname can be found as Underdoun, Underdoune, Underdowne and Underdown. Recordings of the surname from Kent Church Registers include: the christening of Ann, daughter of Richard Underdowne, on November 5th 1570, at St. George the Martyr, Canterbury; the marriage of Richardine Underdown and Symon Marsh at Elham, on November 6th 1592; and the marriage of John Underdown and Martha Hunt at St. John in Thanet, on November 24th 1605. The first recorded spelling of the family name is shown to be that of Wulfwinus Vnderdune, Kent, which was dated 1185, in the "Records of the Templars in England in the 12th Century", during the reign of King Henry 11, known as "The Builder of Churches", 1154 - 1189. 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.