The Home family descends in the male-line from Cospatric I (died after 1073), the Anglo-Celtic Earl of Northumbria. His descendant William de Home (son of Sir Patrick de Greenlaw, the second son of Cospatric III, Earl of Lothian), adopted the surname following his acquisition of the lands of Home in Berwickshire in the early 13th century, through his marriage to his second cousin Ada (the daughter of Patrick I, Earl of Dunbar). William's arms featured the silver lion of Dunbar but with a green field instead of a red field, in reference to his lands of Greenlaw.