to and fro

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adverb Back and forth.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adverb dated Back and forth; with an alternating motion.
• verb dated To go back and forth; to alternate.
• adjective dated Pertaining to something or someone moving forward and back to the same position.
• noun dated The movement (of someone or something) forward followed by a return to the same position. May refer to a concept such as an emotional state or a relationship as well as a physical thing.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adverb moving from one place to another and back again