Welsh surnames

Fixed family names were adopted in Wales from the 15th century onwards. Until this point, the Welsh had a patronymic naming system.

In 1292, 48 percent of Welsh names were patronymics, and in some parishes over 70 percent. Other names were derived from nicknames, (rarely) occupational names, and a few non-hereditary personal names. Patronymic names changed from generation to generation, with a person's baptismal name being linked by ap, ab (son of) or ferch (daughter of) to the father's baptismal name to perhaps the seventh generation. For example, Evan son of Thomas would be known as Evan (ap) Thomas; Evan's son, John, would be John (ab) Evan; John's son Rees would be Rees (ap) John; and David's son, James, would be James (ap) David.

Patronymics were essentially a genealogical history of the family (or its male line), and names such as Llewelyn ap Dafydd ab Ieuan ap Griffith ap Meredith were not uncommon. The Encyclopedia of Wales surmises that the system arose from Welsh law, which made it essential for people to know how people were descended from an ancestor. These laws were decaying by the later Middle Ages, and the patronymic system was gradually replaced by fixed surnames, although the use of patronymic names continued up until the early 19th century in some rural areas. In the reign of Henry VIII surnames became hereditary amongst the Welsh gentry, and the custom spread slowly amongst commoners. Areas where English influence was strong abandoned patronymics earlier, as did town families and the wealthy.

New surnames retained the "ap" in a few cases, mainly in reduced form at the start of the surname, as in Upjohn (from ap John), Powell (from ap Hywel), and Bowen (from ab Owen). Alternatively, the ap was simply dropped entirely. The most common surnames in modern Wales result from adding an s to the end of the name, as in Jones, Roberts and Edwards. Patronymic surnames with the short -s form are recorded in various parts of England dating back to the Middle Ages, and the Welsh practice was presumably in imitation of this. As most Welsh surnames, however, are derived from patronymics, and often based on a small set of first names, Welsh communities are full of families bearing the same surnames, but who are completely unrelated; it cannot be assumed that two people named Jones, even in the same village, must be related. Indeed, currently it is not uncommon that five or more of the starting fifteen for the Welsh international rugby team would be named Jones (all of the following played in that period and are not immediately related to any of the others: Adam R. Jones, Dafydd Jones, Ryan Jones, Stephen Jones, Mark Jones, Adam M. Jones, Alun Wyn Jones, Duncan Jones). The prevalence of names such as Jones, Williams and Thomas brought a need for further distinction and in the 19th century a trend started for double surnames, created by prefixing the name of a house, parish or the mother's surname, as in "Cynddylan Jones". A hyphen was sometimes later introduced, for example "Nash-Williams".

...
Wikipedia