The Collaborative International Dictionary of English v.0.48:

Sup \Sup\ (s[u^]p), v. t. [imp. & p. p. Supped; p. pr. & vb.
   n. Supping.] [OE. soupen to drink, AS. s[=u]pan; akin to D.
   zuipen, G. saufen, OHG. s[=u]fan, Icel. s[=u]pa, Sw. supa,
   Dan. s["o]be. Cf. Sip, Sop, Soup, Supper.]
   To take into the mouth with the lips, as a liquid; to take or
   drink by a little at a time; to sip.
   [1913 Webster]

         There I'll sup
         Balm and nectar in my cup.               --Crashaw.
   [1913 Webster]