Joking aside, I beleive the name Keig/ Kegg/ Mac kyg/ is very old and of celtic origin,The first recorded spelling of the family name is believed to be that of Muircheartach Mac Taidhd which is dated 1159,in the Manx Names Register,during the reign of the High Kings of Ireland 1022-1166.The name has constantly developed and changed over the years.