The Collaborative International Dictionary of English v.0.48:

Sisal grass \Si*sal" grass`\, Sisal hemp \Si*sal" hemp`\,
   The prepared fiber of the Agave Americana, or American
   aloe, used for cordage; -- so called from Sisal, a port in
   Yucatan. See Sisal hemp, under Hemp.
   [1913 Webster]