Yay!
I'm not sure why, but traditionally
Sunny was used as a nn for
Alexandra. Tsarina
Alexandra was called
Sunny (although her birth name was
Alix, a form of
Alice, so that might not be a valid one.) But I also know of
Sunny von Bulow, famous heiress whose husband was tried for her attempted (or was it actual?) murder. Her full name was
Alexandra.
In any event, I associate
Sunny with
Alexandra.
Sandra -->
Sandy -->
Sunny? Who ever knows?
I forgot one combo:
Sunny Louisa. (But someone may already have suggested that one.)