The Collaborative International Dictionary of English v.0.48:

Leech \Leech\, n. [Cf. LG. leik, Icel. l[imac]k, Sw. lik
   boltrope, st[*a]ende liken the leeches.] (Naut.)
   The border or edge at the side of a sail. [Written also
   leach.]
   [1913 Webster]

   Leech line, a line attached to the leech ropes of sails,
      passing up through blocks on the yards, to haul the
      leeches by. --Totten.

   Leech rope, that part of the boltrope to which the side of
      a sail is sewed.
      [1913 Webster]