Zandik (or zindik) was used in Sassanid Persia to denote "heretics", certainly the Manichaeans[1] and possibly other heterodox groups such as the Mazdakites.[2]
The Muslim term zindiq ("heretic, freethinker") applied to heretics or sectants, who are also often said to disbelieve in Allah, deny the resurrection, and not to believe in life after death, was borrowed from Middle Persian zandik.[1][2] Mazdakite, Manichaean and Gnostic communities used to be referred to as "Zindikites".
One possible etymological derivation is that the term alluded to "free interpretation" or "commentary" on the sacred texts, the same root that occurs in the word Zand, referring to the commentary on the Avesta[1][2][3][4][5][6] (cf. Muslim batiniyya). Another view, espoused by the Dehkhoda Persian Dictionary, is that zand is derived from Avestan zanda - a root found in two instances in Avesta (Yasna 61, 3; Vendidad 18, 53-55), which has seemingly implied sinners such as bandits, thieves, enchanters, renegades and liars.
This article incorporates text from the public domain 1907 edition of The Nuttall Encyclopædia.