The Collaborative International Dictionary of English v.0.48:

Forth \Forth\, v.[AS. for[eth], fr. for akin to D. voort, G.
   fort [root]78. See Fore, For, and cf. Afford,
   Further, adv.]
   1. Forward; onward in time, place, or order; in advance from
      a given point; on to end; as, from that day forth; one,
      two, three, and so forth.
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            Lucas was Paul's companion, at the leastway from the
            sixteenth of the Acts forth.          --Tyndale.
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            From this time forth, I never will speak word.
                                                  --Shak.
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            I repeated the Ave Maria; the inquisitor bad me say
            forth; I said I was taught no more.   --Strype.
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   2. Out, as from a state of concealment, retirement,
      confinement, nondevelopment, or the like; out into notice
      or view; as, the plants in spring put forth leaves.
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            When winter past, and summer scarce begun,
            Invites them forth to labor in the sun. --Dryden.
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   3. Beyond a (certain) boundary; away; abroad; out.
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            I have no mind of feasting forth to-night. --Shak.
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   4. Throughly; from beginning to end. [Obs.] --Shak.
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   And so forth, Back and forth, From forth. See under
      And, Back, and From.

   Forth of, Forth from, out of. [Obs.] --Shak.

   To bring forth. See under Bring.
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The Collaborative International Dictionary of English v.0.48:

Back \Back\, adv. [Shortened from aback.]
   1. In, to, or toward, the rear; as, to stand back; to step
      back.
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   2. To the place from which one came; to the place or person
      from which something is taken or derived; as, to go back
      for something left behind; to go back to one's native
      place; to put a book back after reading it.
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   3. To a former state, condition, or station; as, to go back
      to private life; to go back to barbarism.
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   4. (Of time) In times past; ago. "Sixty or seventy years
      back." --Gladstone.
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   5. Away from contact; by reverse movement.
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            The angel of the Lord . . . came, and rolled back
            the stone from the door.              --Matt.
                                                  xxviii. 2.
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   6. In concealment or reserve; in one's own possession; as, to
      keep back the truth; to keep back part of the money due to
      another.
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   7. In a state of restraint or hindrance.
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            The Lord hath kept thee back from honor. --Numb.
                                                  xxiv. 11.
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   8. In return, repayment, or requital.
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            What have I to give you back?         --Shak.
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   9. In withdrawal from a statement, promise, or undertaking;
      as, he took back the offensive words.
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   10. In arrear; as, to be back in one's rent. [Colloq.]
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   Back and forth, backwards and forwards; to and fro.

   To go back on, to turn back from; to abandon; to betray;
      as, to go back on a friend; to go back on one's
      professions. [Colloq.]
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WordNet (r) 3.0 (2006):

back and forth
    adv 1: moving from one place to another and back again; "he
           traveled back and forth between Los Angeles and New
           York"; "the treetops whipped to and fro in a frightening
           manner"; "the old man just sat on the porch and rocked
           back and forth all day" [syn: back and forth, backward
           and forward, to and fro]

Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "back and forth":
   alternate, alternately, back-and-forth, backward and forward,
   backwards and forwards, capriciously, changeably, desultorily,
   erratically, hitch and hike, in and out, inconstantly,
   mutatis mutandis, off and on, on and off, reciprocal, reciprocally,
   reciprocative, ride and tie, round and round, seesaw, shuttlewise,
   sine wave, to and fro, to-and-fro, uncertainly, unsteadfastly,
   unsteadily, up and down, up-and-down, variably, vice versa,
   waveringly