the world > movement > motion in a certain direction > backward movement > [adverb] > in direction originally come from (3)
In the direction from which one has come, towards the place of starting, in the opposite direction from that in which one has advanced.
= back, adv. 5. Cf. abackward, adv.
literal. In the opposite direction in space, so as to return to the place originally left. Often with the verb (go, etc.) omitted: cf. 1.