Zandik was used in Sassanid Persia to denote "heretics", certainly the Manichaeans

Manichaeism

Manichaeism in Modern Persian Āyin e Māni; ) was one of the major Iranian Gnostic religions, originating in Sassanid Persia.Although most of the original writings of the founding prophet Mani have been lost, numerous translations and fragmentary texts have survived...

 and possibly other heterodox groups such as the Mazdak

Mazdak

Mazdak was a proto-socialist Persian reformer and religious activist who gained influence under the reign of the Sassanian Shahanshah Kavadh I...

ites.

The Muslim term zindiq

Zindiq

Zindīq is applied by Muslims to individuals whom are considered to hold views or follows practices that are contrary to central Islamic dogmas...

("heretic, freethinker") applied to heretics

Heresy

Heresy is a controversial or novel change to a system of beliefs, especially a religion, that conflicts with established dogma. It is distinct from apostasy, which is the formal denunciation of one's religion, principles or cause, and blasphemy, which is irreverence toward religion...

 or sectants

Sect

A sect is a group with distinctive religious, political or philosophical beliefs. Although in past it was mostly used to refer to religious groups, it has since expanded and in modern culture can refer to any organization that breaks away from a larger one to follow a different set of rules and...

, who are also often said to disbelieve in Allah

Allah

Allah is a word for God used in the context of Islam. In Arabic, the word means simply "God". It is used primarily by Muslims and Bahá'ís, and often, albeit not exclusively, used by Arabic-speaking Eastern Catholic Christians, Maltese Roman Catholics, Eastern Orthodox Christians, Mizrahi Jews and...

, deny the resurrection

Resurrection

Resurrection refers to the literal coming back to life of the biologically dead. It is used both with respect to particular individuals or the belief in a General Resurrection of the dead at the end of the world. The General Resurrection is featured prominently in Jewish, Christian, and Muslim...

, and not to believe in life after death, was borrowed from Middle Persian zandik. Mazdakite, Manichaean and Gnostic communities used to be referred to as "Zindikites".

Etymology

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

Avesta

The Avesta is the primary collection of sacred texts of Zoroastrianism, composed in the Avestan language.-Early transmission:The texts of the Avesta — which are all in the Avestan language — were composed over the course of several hundred years. The most important portion, the Gathas,...

 (cf. Muslim batiniyya

Batiniyya

Batiniyya is a pejorative term to refer to those groups, such as Alevism, Ismailism, and often Sufism, which distinguish between an inner, esoteric level of meaning in the Qur'an, in addition to the outer, exoteric level of meaning Zahiri...

). Another view, espoused by the Dehkhoda Persian Dictionary

Dehkhoda Dictionary

The Dehkhoda Dictionary is the largest comprehensive Persian dictionary ever published, comprising 15 volumes . The complete work is an ongoing effort that entails over forty-five years of efforts by Dehkhoda and a cadre of other experts.The series initially consisted of 3 million records until...

, is that zand is derived from Avestan zanda - a root found in two instances in Avesta

Avesta

The Avesta is the primary collection of sacred texts of Zoroastrianism, composed in the Avestan language.-Early transmission:The texts of the Avesta — which are all in the Avestan language — were composed over the course of several hundred years. The most important portion, the Gathas,...

 (Yasna

Yasna

Yasna is the name of the primary liturgical collection of texts of the Avesta as well as the name of the principal Zoroastrian act of worship at which those verses are recited. The Yasna, or Izeshne, is primarily the name of the ceremony in which the entire book is recited and appropriate...

 61, 3; Vendidad

Vendidad

The Vendidad or Videvdat is a collection of texts within the greater compendium of the Avesta. However, unlike the other texts of the Avesta, the Vendidad is an ecclesiastical code, not a liturgical manual.-Name:...

18, 53-55), which has seemingly implied sinners such as bandits, thieves, enchanters, renegades and liars.