How surnames began
In Europe, the adoption of hereditary surnames began in the Middle Ages, over the period between about 900 and about 1300 and continued at very different paces in different locations. In Wales, up to the mid 1800s, most people in rural areas used single-generation patronymics, as in Iceland. In Turkey, people were required to use a surname only from 1934.
Initially, surnames were common only among the aristocracy. With literacy and the broadening of government record-keeping, the practice slowly spread among other classes. In urban areas, at least, most surnames were fixed and hereditary by the 1700s.
Into the middle of this in the mid 1100s came the Normans, who as yet had no hereditary surnames themselves. They took up the Irish practice with relish. The De Burgo family, who acquired most of Connacht for themselves, spun off dozens of modern names: (Mc)Davey, (Mc)Davitt, (Mc)Doak, (Mc)Nicholas (Mc)Philbin, McRedmond . all stemming from the forenames of prominent de Burgos, and all following precisely the Gaelic Irish tradition.