  The stiff equation of state (EoS) giving the neutron-star mass of
$2M_{\odot}$ suggests the existence of strongly repulsive many-body effect
(MBE) not only in nucleon channels but also in hyperonic ones. As a specific
model for MBE, the repulsive multi-pomeron exchange potential (MPP) is added to
the two-body interaction together with the phenomenological three-body
attraction. For various versions of the Nijmegen interaction models, the MBE
parts are determined so as to reproduce the observed data of $B_\Lambda$. The
mass dependence of $B_\Lambda$ values is shown to be reproduced well by adding
MBE with the strong MPP repulsion assuring the stiff EoS of hyperon-mixed
neutron-star matter, when $P$-state components of the adopted interaction model
lead to almost vanishing contributions. The nuclear matter $\Lambda\!N$
$G$-matrix interactions are derived and used in $\Lambda$ hypernuclei on the
basis of the averaged-density approximation (ADA). The $B_\Lambda$ values of
hypernuclei with $9 \le A \le 59$ are analyzed in the framework of
Antisymmetrized Molecular Dynamics with use of the two types of $\Lambda\!N$
$G$-matrix interactions including strong and weak MPP repulsions. The
calculated values of $B_\Lambda$ reproduce the experimental data finely within
a few hundred keV. The values of $B_\Lambda$ in $p$-states also can be
reproduced well, when ADA is modified to be suitable also to weakly-bound
$\Lambda$ states.
