The Collaborative International Dictionary of English v.0.48:

Underfong \Un`der*fong"\, v. t. [AS. underfongen, p. p. of
   underf[=o]n to undertake; under under + f[=o]n to take. See
   Fang to seize.]
   1. To undertake; to take in hand; to receive. [Obs.] --Piers
      Plowman. --Rom. of R.
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   2. To insnare; to circumvent. [Obs.] --Spenser.
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   3. To sustain; to support; to guard. [Obs.] --Nash.
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