If we count only three generations to a century, our ancestors were carrying their children or others pick-a-back twelve generations ago and calling the manner by that name, or one very like it.
That is, in the original dialect the term may have been pick pack, which may have referred to a pack picked (pitched) on one’s shoulders.
In the past hundred and fifty years the term has often been corrupted to piggy-back or the like, but great honored men have, on occasion, been carried pickaback; none has yet been carried piggy-back.