A person who practices heathenism or holds heathen beliefs; one who is not Christian or adherent to a major monotheistic religion.
From 'heathen' plus the suffix '-ist' (from Greek '-istes'), which denotes a person who follows or practices something. The term dates to at least the 16th century in religious polemical writing.
Calling someone a 'heathenist' was a way to make non-belief sound like an active ideology rather than simply the absence of Christianity—a rhetorical move that gave more weight to the opposition.
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