  We present a scenario that the multi-component fluctuations, especially those
of the spin-orbital coupled modes, lead to the mass enhancement observed in
LiV_2O_4. This phenomena is possible because all these modes are fluctuating
due to the geometrical frustration. To illustrate this mechanism, the
t_{2g}-orbital Hubbard model on the pyrochlore lattice is studied based on the
random-phase approximation. We derive the generalized susceptibility in the
SU(6) spin-orbital space and calculate the free energy by using a
coupling-constant integration. The estimated specific heat coefficient is of
the correct order of magnitude to explain the experiment.
