An Etymological Dictionary of Astronomy and Astrophysics

To burden with cruel or unjust impositions or restraints; subject to a burdensome or harsh exercise of authority or power (Dictionary.com).

Etymology (EN): M.E. oppressen, from O.Fr. opresser “oppress, torment, smother,” from M.L. oppressare, from L. opprimere “press against, press together, press down; subdue, prosecute relentlessly,” from op variant of ob “against” + premere “to press, hold fast.”

Etymology (PE): Infinitive from setam, → oppression.