The Collaborative International Dictionary of English v.0.48:

Wane \Wane\, v. i. [imp. & p. p. Waned; p. pr. & vb. n.
   Waning.] [OE. wanien, AS. wanian, wonian, from wan, won,
   deficient, wanting; akin to D. wan-, G. wahnsinn, insanity,
   OHG. wan, wana-, lacking, wan?n to lessen, Icel. vanr
   lacking, Goth. vans; cf. Gr. ? bereaved, Skr. ?na wanting,
   inferior. ????. Cf. Want lack, and Wanton.]
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   1. To be diminished; to decrease; -- contrasted with wax,
      and especially applied to the illuminated part of the
      moon.
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            Like the moon, aye wax ye and wane.
            Waning moons their settled periods keep. --Addison.
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   2. To decline; to fail; to sink.
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            You saw but sorrow in its waning form. --Dryden.
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            Land and trade ever will wax and wane together.
                                                  --Sir J.
                                                  Child.
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