The Collaborative International Dictionary of English v.0.48:

Tug \Tug\, v. t. [imp. & p. p. Tugged; p. pr. & vb. n.
   Tugging.] [OE. toggen; akin to OD. tocken to entice, G.
   zucken to jerk, draw, Icel. toga to draw, AS. t['e]on, p. p.
   togen, to draw, G. ziehen, OHG. ziohan, Goth. tiuhan, L.
   ducere to lead, draw. Cf. Duke, Team, Tie, v. t.,
   Touch, Tow, v. t., Tuck to press in, Toy a
   plaything.]
   1. To pull or draw with great effort; to draw along with
      continued exertion; to haul along; to tow; as, to tug a
      loaded cart; to tug a ship into port.
      [1913 Webster]

            There sweat, there strain, tug the laborious oar.
                                                  --Roscommon.
      [1913 Webster]

   2. To pull; to pluck. [Obs.]
      [1913 Webster]

            To ease the pain,
            His tugged cars suffered with a strain. --Hudibras.
      [1913 Webster]