1
general::
Phrase(s): to and fro
[of movement] toward and away from something. • The puppy was very active—running to and fro— wagging its tail. • The lion in the cage moved to and fro, watching the people in front of the cage.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Back and forth, as in He was like a caged animal, pacing to and fro. Strictly speaking, to means "toward" and fro "away from," but this idiom is used more vaguely in the sense of ‘‘moving alternately in different directions." [First half of 1300s]
American Heritage Idioms