Guinness

The name mcGuinness is Irish Gaelic - mc Aonghusa meaning the son of Aongus who was of the Dal Airaidhe in Gaelic Ulster. This is one of the Gaelic tribes from Ireland (Scoti) who invaded western Caledonia and what is now known as Scotland (Scoti-land). They and other Gaels from Ireland created the great kingdom of Dal Riada before eventually assimilating with the Picts. That is how the name mcGuinness, Macinnis, Maginnis, etc etc arrived in Scotland.