to nail an assertion

from The Collaborative International Dictionary of English v.0.48
Nail \Nail\, v. t. [imp. & p. p. {Nailed} (n[=a]ld); p. pr. &
   vb. n. {Nailing}.] [AS. naeglian. See {Nail}, n.]
   1. To fasten with a nail or nails; to close up or secure by
      means of nails; as, to nail boards to the beams.
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            He is now dead, and nailed in his chest. --Chaucer.
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   2. To stud or boss with nails, or as with nails.
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            The rivets of your arms were nailed with gold.
                                                  --Dryden.
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   3. To fasten, as with a nail; to bind or hold, as to a
      bargain or to acquiescence in an argument or assertion;
      hence, to catch; to trap.
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            When they came to talk of places in town, you saw at
            once how I nailed them.               --Goldsmith.
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   4. To spike, as a cannon. [Obs.] --Crabb.
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   {To nail an assertion} or {To nail a lie}, etc., to detect
      and expose it, so as to put a stop to its currency; -- an
      expression probably derived from the former practice of
      shopkeepers, who were accustomed to nail bad or
      counterfeit pieces of money to the counter.
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