Cheerful but laidback, surname-style Delaney is derived from the Old Irish name Dubhshláine and has become a familiar choice for girls in recent decades. Nevertheless, it has also been used for boys since the early 1900s and was equally - though rarely - given to both, right up until the 1990s.

Billie as a masculine name originated as a diminutive form of William, derived from Germanic elements meaning "will" or "determination" and "helmet" or "protection." While more commonly recognized as a feminine name today, Billie has historical precedence as a male name, particularly in the early to mid-20th century. Notable male bearers include jazz musician Billie Holiday (born Eleanora but adopted the masculine spelling) and various athletes and musicians. The name conveys a friendly, approachable quality with vintage charm. Though its popularity for boys has declined significantly since the 1960s, it maintains appeal for parents drawn to gender-neutral naming options with traditional roots and a casual, unpretentious character.