  An essential step towards the identification of a fermion mass generation
mechanism at Planck scale is to analyse massive fermions in a given quantum
gravity framework. In this letter the two mass terms entering the Hamiltonian
constraint for the Einstein-Majorana system are studied in the loop
representation of quantum gravity and fermions. One resembles a bare mass gap
because it is not zero for states with zero (fermion) kinetic energy as
opposite to the other that is interpreted as `dressing' the mass. The former
contribution originates from (at least) triple intersections of the loop states
acted on whilst the latter is traced back to every couple of coinciding end
points, where fermions sit. Thus, fermion mass terms get encoded in the
combinatorics of loop states. At last the possibility is discussed of relating
fermion masses to the topology of space.
