Word Origin and History for born on the wrong side of blanket
c.1300, from O.Fr. blanchet, dim. of blanc "white" (see blank). Originally "a white cloth" (a secondary sense of O.Fr. blanc). The verb is first recorded c.1600. Wet blanket (1830) is from the notion of a person who throws a damper on social situations like a wet blanket smothers a fire.