contusion (n.)

c. 1400, "act of beating or bruising; a bruise, an injury to the body without apparent wound or fracture," from Latin contusionem (nominative contusio) "a crushing, breaking, battering," in medical language, "a bruise," noun of action from past-participle stem of contundere "to beat, bruise, grind, crush, break to pieces," from assimilated form of com-, here perhaps an intensive prefix (see com-), + tundere "to beat" (see obtuse).