Recorded in several forms including Masden, Masedon, Massedon, Masding, Masdon and Mazdon, this is an English surname. It is locational, and almost certainly a dialectal variant of the popular Yorkshire village name Marsden, first recorded in the 13th century. According to all the known gazetters of the British Isles no such place as Masden or Masdon or any of the known surname spellings, exists or has existed. The possibility remains that it could derive from a now 'lost' medieval place of which the only public reminder in the 20th century is the surname, in all its spellings. Some five thousand surnames of the British isle derive from 'lost' villages, so this is a possibility. Locational surnames are 'from' names. This is to say that they were usually given to people after they left their original homes, and moved elsewhere. The further they moved, the more likely that the spelling form moved away from the original. In this case the London church registers show a steady series of changes over three centuries. These developed recordings examples commence with John Masden, a witness at the church of St Margarets, Westminster, on August 13th 1619, then Jane Masdon, who married Francis Dunhame (!) on December 23rd 1681, then Miles Mazden, christened at St Martins in the Field, Trafalgar Square, on April 19th 1718, and finally Lydia Maria Mazdon, who married Charles Fordham, at Christ Church, Southwark, on October 5th 1850.