The Collaborative International Dictionary of English v.0.48:

Wherefore \Where"fore\, adv. & conj. [Where + for.]
   [1913 Webster]
   1. For which reason; so; -- used relatively.
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            Wherefore by their fruits ye shall know them.
                                                  --Matt. vii.
                                                  20.
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   2. For what reason; why; -- used interrogatively.
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            But wherefore that I tell my tale.    --Chaucer.
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            Wherefore didst thou doubt?           --Matt. xiv.
                                                  31.
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The Collaborative International Dictionary of English v.0.48:

Wherefore \Where"fore\, n.
   the reason why. [Colloq.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

wherefore
    n 1: the cause or intention underlying an action or situation,
         especially in the phrase `the whys and wherefores' [syn:
         why, wherefore]

Moby Thesaurus II by Grady Ward, 1.0:

80 Moby Thesaurus words for "wherefore":
   accordingly, after all, after which, all things considered,
   argument, because of that, because of this, before the bench,
   before the court, ceteris paribus, consequently, considering, ergo,
   everything being equal, excuse, explanation, for that,
   for that cause, for that reason, for this cause, for this reason,
   for which, for which reason, for why, from what cause, ground,
   hence, hereat, hereinafter, how come, in court, on, on balance,
   on that account, on that ground, on the whole, on this account,
   on what account, pourquoi, pretense, pretext, proof, propter hoc,
   rational ground, rationale, reason, reason for, reason why,
   stated cause, sub judice, taking into account, the big idea,
   the idea, the whatfor, the wherefore, the why, then, thence,
   thereat, therefor, therefore, this being so, thus, thusly,
   thuswise, underlying reason, upon, upon which, what for, whence,
   whereat, wherefrom, whereon, whereto, whereunto, whereupon,
   wherewith, why, whyever, whyfor