  We investigate a tunneling and emission process of a thin-shell from a
Schwarzschild black hole, where the shell was initially located beyond the
Einstein-Rosen bridge and finally appears at the right side of the Penrose
diagram. In order to obtain such a solution, we should assume that the areal
radius of the black hole horizon increases after the tunneling. Hence, there is
a parameter range such that the tunneling rate is exponentially enhanced,
rather than suppressed. We may have two interpretations regarding this. First,
such a tunneling process from the past horizon is improbable by physical
reasons; second, such a tunneling is possible in principle, but in order to
obtain a stable Einstein-Rosen bridge, one needs to restrict the parameter
spaces. If such a process is allowed, this can be a non-perturbative
contribution to Einstein-Rosen bridges as well as eternal black holes.
