Are yams and sweet potatoes the same?
early 13c., of a wheel, "to rotate, roll over," from over- + turn (v.). Attested from c.1300 in general transitive sense "to throw over violently;" figurative meaning "to ruin, destroy" is from late 14c. Of judicial decisions, "to reverse," it is attested from 1826. Related: Overturned; overturning.