English last names: more than meets the eye.
Over time, some countries developed specific rules, publishing 'Naming Systems' for use in developing surnames. These systems, for example, promoted the use of suffixes like I, II, or III, which when used, the eldest son's name could be the same as that of the father. The Normans also introduced the Sr. and Jr. suffixes to distinguish father and son.
Regionally there are commonalties among the way heritable surnames were derived. The English terminated names with 'son', 'ing', and 'kin', which are comparable to names prefixed with the Gaelic 'Mac', the Norman 'Fitz', the Irish '0', and the Welsh 'ap'. There are also German, Dutch, Scandinavian, and other European surnames of similar formation, such as the Scandinavian names ending in 'sen'. In the Slavic countries, the 'sky' and 'ski' played the same role.
The Italians used a variety of prefixes for their naming practices. The prefix 'di' (meaning 'of') was often attached to an otherwise ordinary Christian name to form a patronym; 'da' and 'di' (meaning 'from') often associated a place of origin; and 'la' and 'lo' (meaning 'the') often derived from nicknames.
While these are examples of a structured approach to naming descendants, all too often other circumstances existed and our ancestors opted for (or were forced into) an alternate approach.