  We compare the results of a numerical lattice QCD calculation of the
charmonium spectrum with the structure of a general non-relativistic potential
model. To achieve this we form the non-relativistic reduction of
derivative-based fermion bilinear interpolating fields used in lattice QCD
calculations and compute their overlap with c-cbar meson states at rest
constructed in the non-relativistic quark model, providing a bound-state model
interpretation for the lattice data. Essential gluonic components in the
bound-states, usually called hybrids, are identified by considering
interpolating fields that involve the gluonic field-strength tensor and which
have zero overlap onto simple c-cbar model states.
