The Collaborative International Dictionary of English v.0.48:

Hobnob \Hob"nob`\, v. i. [imp. & p. p. Hornobbed; p. pr. & vb.
   n. Hornobbing.]
   1. To drink familiarly (with another). [ Written also
      hob-a-nob.]
      [1913 Webster]

   2. To associate familiarly; to be on intimate terms; as, to
      hobnob with the political elite.
      [1913 Webster]