  We study the appearance of a sharp collective mode which features transverse
current fluctuations within the bosonization approach to interacting
two-dimensional Fermi liquids. This mode is analogous to the shear sound modes
in elastic media, and, unlike the conventional zero sound mode, it is damped in
weakly interacting Fermi liquids and only separates away from the particle-hole
continuum when the quasiparticle mass becomes twice the transport mass $m^*
\gtrsim 2 m$. The shear sound should be present in a large class of interacting
charged and neutral Fermi liquids especially those proximate to critical points
where the quasiparticle mass diverges. In metals this mode remains linearly
dispersing in the presence of the long-ranged Coulomb force, unlike the
conventional zero sound mode which becomes the plasma mode. We also detail a
quick path between bosonization and classical Landau's Fermi liquid theory by
constructing a mapping between the solutions of the classical kinetic equation
and the quantized bosonic eigenmodes. By further mapping the kinetic equation
into a 1D tight-binding model we solve for the entire spectrum of collective
and incoherent particle-hole excitations of Fermi liquids with non-zero $F_0$
and $F_1$ Landau parameters.
