The Collaborative International Dictionary of English v.0.48:

Tipple \Tip"ple\, v. i. [imp. & p. p. Tippled; p. pr. & vb. n.
   Tippling.] [From tip a small end, or a word akin to it; cf.
   Norw. tipla to tipple, to drip, Prov. E. tip, tiff, tift, a
   draught of liquor, dial. G. zipfeln to eat and drink in small
   parts. See Tip a point, and cf. Tipsy.]
   To drink spirituous or strong liquors habitually; to indulge
   in the frequent and improper used of spirituous liquors;
   especially, to drink frequently in small quantities, but
   without absolute drunkeness.
   [1913 Webster]

         Few of those who were summoned left their homes, and
         those few generally found it more agreeable to tipple
         in alehouses than to pace the streets.   --Macaulay.
   [1913 Webster]