The Collaborative International Dictionary of English v.0.48:

Couth \Couth\ (k??th), imp. & p. p. of Can. [See Can, and
   cf. Uncouth.]
   Could; was able; knew or known; understood. [Obs.]
   [1913 Webster]

         Above all other one Daniel
         He loveth, for he couth well
         Divine, that none other couth;
         To him were all things couth,
         As he had it of God's grace.             --Gower.
   [1913 Webster]

WordNet (r) 3.0 (2006):

couth
    adj 1: (used facetiously) refined