As a family name, Kelly has many origins. The family name started in the 19th century. It was used for a masculine name in the late 19th century. Feminine use began around 1940. By 1957, it surpassed male usage thanks to American actress Grace Kelly.
Kelly, as a girl's name, was at #900 in 1950. It peaked at #10 around 1977. Kelly is still popular as a girl's name, although it has declined.