  We propose a self-interacting inelastic dark matter (DM) scenario as a
possible origin of the recently reported excess of electron recoil events by
the XENON1T experiment. Two quasi-degenerate Majorana fermion DM interact
within themselves via a light hidden sector massive gauge boson and with the
standard model particles via gauge kinetic mixing. We also consider an
additional long-lived singlet scalar which helps in realising correct dark
matter relic abundance via a hybrid setup comprising of both freeze-in and
freeze-out mechanisms. While being consistent with the required DM
phenomenology along with sufficient self-interactions to address the small
scale issues of cold dark matter, the model with GeV scale DM can explain the
XENON1T excess via inelastic down scattering of heavier DM component into the
lighter one. All these requirements leave a very tiny parameter space keeping
the model very predictive for near future experiments.
