What is "to nail an assertion"

Nail \Nail\, v. t. [imp. & p. p. Nailed (n[=a]ld); p. pr. & vb. n. Nailing.] [AS. n[ae]glian. 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.

   He is now dead, and nailed in his chest.
   --Chaucer.

2. To stud or boss with nails, or as with nails.

   The rivets of your arms were nailed with gold.
   --Dryden.

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.

   When they came to talk of places in town, you saw at once how I nailed them.
   --Goldsmith.

4. To spike, as a cannon. [Obs.]
   --Crabb.

   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.