What does Nishka mean?
From the Sanskrit निष्क (niṣka), an ancient gold coin, and by extension a golden necklace or ornament — attested in the Manusmriti and other classical texts. Popular 'pure/honest' glosses on name sites are not supported by the classical sources.
What does Vaishnavi mean?
From the Sanskrit वैष्णवी (vaiṣṇavī), feminine of Vaishnava, 'relating to Vishnu'. It denotes a female devotee of Vishnu and is also the name of the Shakti (divine energy) of Vishnu, one of the Sapta Matrikas.