Recorded in many forms including MacGenis, McGinnis, MaGennis, MacGuiness, McGuiness, McGuinness, Guiness, Guinness, and others, this is a famous name. It is arguably of both Scottish, Irish, and Manx origins, being derived from the early spelling of 'MagAonghusa'. This is considered to be an early form of the personal name Angus from 'aon' meaning one and '-gus', enterprise. As such Aonghusa means literally 'Unique enterprise'. The first bearer of the name is believed to be Aonghus Turimleach, one of three Irish brothers, who invaded Scotland in the 3rd century a.d, and gave his name to the district and county of Angus. The ancestry of the Irish MacGuinness family is claimed to be traceable back to the 5th century a.d, although this is certainly open to conjecture. What is certain is that by the start of the Medieval Period in the 12th century they had become territorial lords of Iveagh in County Down, with their fortress at Rathfriland. Several of the clan fought with Hugh O' Neill at the victorious battle of the Yellow Ford in 1598. The present chief Lord Iveagh was until recently president of Guinness of Dublin, set up by Arthur Guinness in 1759, and at various times the largest brewery in the world. The first recorded spelling of the family name is shown to be that of Mag Aonghusa. This was dated 1150 a.d., in the Early Records of Iveagh, County Down, Ireland, during the reign of Turlough Mor O' Connor, High King of Ireland, 1119 - 1156. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.