It could be a variety of
Anisa, which is Arabic for "friendly", or a derivative of
Annis, which in turn ia a derivative of
Agnes, which means "chaste". Also, it could come from
Anissa, which is
Anna combined with the suffix -issa. Maybe it comes from
Anise, but that's not very likely.
There is a user-submitted name that matches Anisha; it says there it's Indian, and means "continuous".