English.

Shirley was originally only a male name, from the Old English "bright wood" or "bright clearing". The use as a female name seems to date from Charlotte Brontë's 1849 novel "Shirley". This is about a family who were sure they would have a boy and had chosen the name Shirley before the birth. When a girl was born they decided to stick with the chosen name for their daughter and this quickly became the more generally accepted use!