The Collaborative International Dictionary of English v.0.48:

Slyboots \Sly"boots`\, n.
   A humerous appellation for a sly, cunning, or waggish person.
   [1913 Webster]

         Slyboots was cursedly cunning to hide 'em. --Goldsmith.
   [1913 Webster]

WordNet (r) 3.0 (2006):

slyboots
    n 1: a shifty deceptive person [syn: dodger, fox,
         slyboots]