It has also been used as a feminine nickname for etymologically unrelated names such as Lillian.
The spelling Billie has recently become primarily feminine in use, while the spelling Billy is more commonly used for males.
[1] Billie has been in use as an independent name for both American girls and boys since the 19th century.
It has been more commonly used for American girls since the early 1990s.
The name has also been commonly used for girls in Australia, Belgium, Canada, France, Ireland, Netherlands, and the United Kingdom.