The Collaborative International Dictionary of English v.0.48:

Con \Con\, v. t. [imp. & p. p. Conned; p. pr. & vb. n.
   Conning.] [AS. cunnan to know, be able, and (derived from
   this) cunnian to try, test. See Can, v. t. & i.]
   1. To know; to understand; to acknowledge. [Obs.]
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            Of muses, Hobbinol, I con no skill.   --Spenser.
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            They say they con to heaven the highway. --Spenser.
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   2. To study in order to know; to peruse; to learn; to commit
      to memory; to regard studiously.
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            Fixedly did look
            Upon the muddy waters which he conned
            As if he had been reading in a book.  --Wordsworth.
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            I did not come into Parliament to con my lesson.
                                                  --Burke.
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   To con answer, to be able to answer. [Obs.]

   To con thanks, to thank; to acknowledge obligation. [Obs.]
      --Shak.
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