According to the ΛCDM framework, clusters grow through accretion of individual galaxies and galaxies in groups, where they may be pre-processed. It thus becomes challenging for us to isolate and study the environmental effects solely due to the cluster host halo. Dwarf early-type galaxies (dEs) can provide us with statistically meaningful testbeds for investigating environmental effects thanks to their high number density and shallow potential well in the Local Universe. To study the imprint of pre-processing on the stellar population content of dEs, we analyzed a sample of nine Virgo dEs that, based on their distribution on the projected phase-space diagram and predictions from N-body simulations, have been accreted to Virgo as gravitationally bound members of a massive galaxy group, about 2-3 Gyr ago. We derived stellar population properties of these dEs (i.e., their age, [M/H] and [α/Fe]) using their MUSE spectra. We found that the dEs of our sample are considerably [α/Fe] enhanced and metal-poorer than equally-massive dEs of the Coma and Virgo clusters that have similar or even larger infall times. We also noted that 6 out of 9 dEs have experienced enhanced star formation (SF) at their accretion time or later, possibly due to shocks and thermal instabilities exerted by ram pressure inside Virgo. According to our results, the rest of our sample was accreted onto Virgo already quenched. Based on our results, we speculate that the short episode of star formation, occurred at infall into Virgo, might be responsible for the relatively high [α/Fe] ratios observed in these six dEs of our sample. Our sample of dEs exhibit on average, a negative metallicity gradient and a positive [α/Fe] gradient. Except for two dEs in our sample, the rest show a flat age gradient. These results are consistent with an inside-out formation scenario, and are in agreement with other observational and theoretical studies in the literature. In this talk, we take advantage of our results and discuss how pre-processing in previous host halos, and early processing in clusters may affect the physical properties of cluster dEs.