jog (v.)
1540s, "to shake up and down," perhaps altered from Middle English shoggen "to shake, jolt, move with a jerk" (late 14c.), of uncertain origin. Meanings "shake," "stir up by hint or push," and "walk or ride with a jolting pace" are from 16c. The main modern sense in reference to running as training mostly dates from 1948; at first a regimen for athletes, it became a popular fad c.1967. Perhaps this sense is extended from its use in horsemanship.
Jogging. The act of exercising, or working a horse to keep him in condition, or to prepare him for a race. There is no development in jogging, and it is wholly a preliminary exercise to bring the muscular organization to the point of sustained, determined action. [Samuel L. Boardman, "Handbook of the Turf," New York, 1910]
Related: Jogged; jogging. As a noun from 1610s.