  We present and discuss the stellar kinematics and populations of the S0
galaxy FCC 170 (NGC 1381) in the Fornax cluster, using deep MUSE data from the
Fornax 3D survey. We show the maps of the first four moments of the stellar
line-of-sight velocity distribution and of the mass-weighted mean stellar age,
metallicity and [Mg/Fe] abundance ratio. The high-quality MUSE stellar
kinematic measurements unveil the structure of this massive galaxy: a nuclear
disk, a bar seen as a boxy bulge with a clear higher-velocity-dispersion X
shape, a fast-rotating and flaring thin disk and a slower rotating thick disk.
Whereas their overall old age makes it difficult to discuss differences in the
formation epoch between these components, we find a clear-cut distinction
between metal-rich and less [Mg/Fe]-enhanced populations in the thin-disk,
boxy-bulge and nuclear disk, and more metal-poor and [Mg/Fe]-enhanced stars in
the thick disk. Located in the densest region of the Fornax cluster, where
signs of tidal stripping have been recently found, the evolution of FCC 170
might have been seriously affected by its environment. We discuss the
possibility of its "pre-processing" in a subgroup before falling into the
present-day cluster, which would have shaped this galaxy a long time ago. The
thick disk displays a composite star formation history, as a significant
fraction of younger stars co-exist with the main older thick-disk population.
The former sub-population is characterized by even lower-metallicity and
higher-[Mg/Fe] values, suggesting that these stars formed later and faster in a
less chemically evolved satellite, which was subsequently accreted. Finally, we
discuss evidence that metal-rich and less [Mg/Fe]-enhanced stars were brought
in the outer parts of the thick disk by the flaring of the thin disk.
