The Collaborative International Dictionary of English v.0.48:

Flip \Flip\ (fl[i^]p), n. [Cf. Prov. E. flip nimble, flippant,
   also, a slight blow. Cf. Flippant.]
   A mixture of beer, spirit, etc., stirred and heated by a hot
   iron.
   [1913 Webster]

   Flip dog, an iron used, when heated, to warm flip.
      [1913 Webster]