The “ap” that hides inside
Wales stuck with patronymics — “son of” names — long after the rest of Britain, using ap (or ab) meaning “son of.” When surnames finally fixed, the ap often fused onto the father’s name: ap Rhys became Price, ap Hywel became Powell, ab Owen became Bowen, ab Evan became Bevan. Spot the surviving p or b and you can often see the father’s name inside.
-s patronymics and nicknames
The other big group adds an English-style -s (“son of”): Jones (son of John), Williams, Davies, Evans. A few are descriptive — Lloyd, “grey”; Vaughan, “the younger.”