Anastasia, whom she nicknamed Shvybzik (a German colloquialism meaning 'little mischief')
OK who wants to play 'guess the word' with me? Because all I can think of is 'Schuft' which is an odd nickname for a child.
Google-Fu also offers two other explanations:
from the German 'beschwipst' (tipsy) again odd for a child
or actually not German but Russian for imp(ish).
Any other ideas?"