This unusual name is of medieval Scottish origin and is locational from a place so called in Aberdeenshire, Scotland. The derivation is from the Northern Middle English 'mor(e)', moorland, with 'dene', a valley, thus 'a moorland valley'. During the Middle Ages as it became more common for people to migrate from their birthplace, generally to seek work elsewhere, they would often adopt the placename as a means of identification, thus resulting in a wide dispersal of the name. James Muirden was a member of the Huntly Corps of Volunteers in 1798 and James Morden (a variant spelling) was a member of the Gartly Company of Volunteers in the same year. Among the recordings in Aberdeenshire is the christening of Adam Muirden on February 23rd 1738 at Old Meldrum. The first recorded spelling of the family name is shown to be that of William Muirden (christening), which was dated 1732, Old Meldrum, Aberdeenshire, during the reign of King George 11, 'The Last Warrior King', 1727-1760. 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.