The Collaborative International Dictionary of English v.0.48:

Stum \Stum\, v. t. [imp. & p. p. Stummed; p. pr. & vb. n.
   Stumming.]
   To renew, as wine, by mixing must with it and raising a new
   fermentation.
   [1913 Webster]

         We stum our wines to renew their spirits. --Floyer.
   [1913 Webster]