Jackson means "son of Jack." In medieval England Jack was the everyday pet form of John (sometimes overlapping with Jacob), so Jackson is a cousin to Johnson: same given-name root, different nickname path into a hereditary surname.
It is intensely common in England and in the United States, including among African American families whose surnames often reflect the wider English naming stock of the South and elsewhere. The type is parent's name—no blacksmith shop required to explain the label, only a father or ancestor called Jack.