What's mean of ”boleyn” ?

Boleyn is indeed just a surname.

The Other Boleyn Girl is the title of the fiction, which the film is based on. Anne Boleyn was the second wife of Henry VIII until she was executed by none other than her own husband. The fiction circles around the rise and fall of the two Boleyn sisters, Anne and Mary. In particular, the author wrote about an affair between the lesser known Mary Boleyn and Henry VIII. Hence, the title of the book is The Other Boleyn Girl highlighting the fact it is not about the once Queen, Anne Boleyn.

Mind you that it is after all a historical fiction. Much of the book was made up by the author and placed into historical context. There is no evidence of such an affair between Mary Boleyn and Henry VIII.

Boleyn
From Wikipedia, the free encyclopedia
Originally "Bullen", Boleyn is the surname of a noble English family particularly prominent in the Tudor period, members of which include:
* Anne Boleyn, the second wife of Henry VIII
* Mary Boleyn, Anne's lesser-known sister

so for this movie ----
Natalie Portman... Anne Boleyn
she turned civilian to a queen , and died.
Scarlett Johansson... Mary Boleyn
the surname ... <--- is the Boleyn girl !!

這部宮闈劇的背景, 是英王亨利八世的妻子 安.博林 (ANNE BOLEYN), 和她的姐姐瑪麗.博林 (MARY BOLEYN) 的宮廷爭寵故事.
電影的名稱 The Other Boleyn Girl, 字面是 "另一名姓博林的女子", 帶出了故事的主軸, 就是國王娶一名姓博林的女子為后 (ANNE), 同時又納另一名姓博林的女子為情婦 (MARY), 因而引發出的曲折鬥爭

According to my understanding, Boleyn is just a surname.