Lewis & Short

con-callesco, callui, 3, v. inch. [calleo]; lit., to become hard or callous; hence, trop.,

  1. * I. Of the intellect, to become shrewd, practised (cf. calleo, I.): callidos eos appello, quorum, tamquam manus opere, sic animus usu concalluit, Cic. N. D. 3, 10, 25.
  2. * II. Of the feelings, to become insensible, obtuse: locus ille animi nostri, stomachus ubi habitabat olim, concalluit, Cic. Att. 4, 16, 10.