Sissie

Sissie is an English pet form and diminutive of sister, used as a familiar given name, particularly in the nineteenth and early twentieth centuries. It arose from the affectionate nursery word sissie or sissy, applied to a sister or a gentle, sweet-natured girl. The name is closely related to the variant Sissy and has also served as a nickname for names beginning with the sound, such as Cecily or Cecilia.