Just ran across that word in my trade journal 'Vacuum Technology and Coating'' which I get monthly.
The article is X-Ray photoelectron spectroscopy and auger electron spectroscopy, comparison and basic principles by Wang and Linford, contributing editors.
These (perturbutions of atoms as the result of electrons slamming into them, my words) are often observed in organic molecules that contain aromatic (benzene-like) moieties.
So Moiety or moieties means parts of a larger molecule, like benzene rings that are assembled together within a larger assembly of molecules, so moiety can be thought of as sub-assemblies of a larger part.
It is also used in anthropology to describe separation of a main group of people like the caste system in India or the Aborigines in Australia.