1
general::
Also, settle or wipe out an old score or scores. Get even, avenge a grievance or an injury. For example, Wendy settled an old score with Bill when she made him wait for half an hour in the rain. These expressions, dating from the mid-1800s to early 1900s, all use score in the sense of "an account" or "bill." Also see PAY OFF, def. 3.
American Heritage Idioms