Premise: Bronwen (] ) is a Welsh feminine given name. It is closely associated with the similar name "Branwen", which appears in medieval Welsh literature. Used in Wales since the 19th century, it was introduced to the English-speaking public at large by a character in the Richard Llewellyn novel "How Green Was My Valley" (1939).
Hypothesis: Richard Llewellyn used the name in his book because it was his daughter's name.