Dynasty, in the sense of naming a dynasty, was passed down by the father/male line only. William I was the first Norman king (so called because he was Duke of Normandy), and his sons were therefore Norman dynasty as well, as would be any children they had. His daughters would themselves be Norman dynasty (for example, if Matilda had successfully ruled in her own right), but their children would not be - they would inherit the dynasties of their fathers. When Stephen took over, he was no longer Norman dynasty, since his connection to William I was through his mother, Adela. He was, instead, the Blois dynasty, after his father, the count of Blois. When Henry II took the throne, Matilda's son, he was the first Angevin dynasty king, since his father was count of Anjou.

This pattern continued all the way until the current monarch. Queen Elizabeth II made a royal proclamation that her children would retain her dynasty (Windsor), rather than that of their father (Mountbatten). It isn't so much that the source of authority can't be derived through the woman's side, but that the house name itself changes, just like a last name traditionally does these days upon marriage - with any children taking the last name of their father.