What is "to con thanks"

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.]

   Of muses, Hobbinol, I con no skill.
   --Spenser.

   They say they con to heaven the highway.
   --Spenser.

2. To study in order to know; to peruse; to learn; to commit to memory; to regard studiously.

   Fixedly did look Upon the muddy waters which he conned As if he had been reading in a book.
   --Wordsworth.

   I did not come into Parliament to con my lesson.
   --Burke.

   To con answer, to be able to answer. [Obs.]

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