From the German girls name Franziska, the feminine form of Franz. The term ziska has become used to describe a girl who is an individual and always up for a party. Often described as both 'weird' and 'sexy', the ziska is usually the girl left wanting more when the party is over.
'dude, why is that girl making cat noises?' 'I don't know, but damn she's partying the shit outta this place, must be a ziska'