This unusual name is of Scottish, Gaelic origin, and is the Anglicized form of the Gaelic 'Mac Coise', the patronymic ('mac' or the contracted 'mc' indication 'son of') from the byname, or nickname, 'cos', meaning 'the footsoldier', or 'the courier or messenger'. In Scotland the name is found most frequently in Ayrshire, although the unusually early first recording of the surname is from Ulster, evidence of the frequently exchange of trade etc., between Scotland and Ireland. Records of 'Gavin Ros' in Edinburgh show John, Patrick and Donald McCosch as voters in the parish of Coylton in 1513, and one John Makcosche was tenant in lands of Hoilmark in the barony of Uchiltrie in 1586. Dr. James McCosh (1811 - 1894), born in Scotland, was principal of Princeton College New Jersey, in America. The first recorded spelling of the family name is shown to be that of Erard mac Coisse, which was dated 990, Annals of Ulster, during the reign of King Constantine IV, King of Scotland, 970 - 994. 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.