I'm not familiar with the term in Anthropology, but I do know that in Republic the Platonic Socrates uses the Greek word Doxa in reference to unsubstantiated beliefs, and contrasts it to Episteme which means 'justified true belief'.

Essentially, Plato draws a distinction between the seeming, and being of things and knowledge, positing that Episteme is the only 'true knowledge', and that Doxa are merely the shadows on the wall of "the Cave".

This seeming/being opposition allows the Platonic Socrates to interrogate the normalized constructs of Greek life: i.e. the masculine virtue of wartime excellence or 'arete', the immanent inferiority of women, the body as the locale of self, and the embedded nature of epic poetry in the mimetic culture of Greece.

Further, Plato's Republic, whether it be the "Just City" or "Kallipolis", is organized around this notion of a proto-transcendental idyllic 'Good'. This concept of the Eidos, or 'form of the Good/Just/Truth' is delivered to us by way of the Doxa/Episteme distinction.

By engaging with the anti-ocular vision of 'truth', the Platonic Socrates places 'true knowledge' outside the reach of most humans - in that, though reason resides within us all, humans have a varying capacity to engage with the Real by means of reason. A well ordered soul, one ruled by reason, would be capable of exploring 'the Good' through Elenchus (Socratic Method) with other enlightened souls. Those enlightened Souls are the Philosopher Kings/Queens of "Kallipolis".

TL;DR: Doxa or seeming, is the foil to the Platonic 'Truth' described in the Theory of Forms. I assume the Anthropological word comes from this Greek origin.