What does Sly mean?
Sly \s-ly\ as a name for boys is of Latin derivation, and the name Sly means "of the woods". Sly is a variant of Sylvester (Latin): the name is associated with a cartoon cat in modern times. Seldom used as a given name for boys.
Sly is an uncommonly occurring first name for men but a very prominent last name for both adults and children (#9630 out of 88799, Top 11%). (2000 U.S. Census)
Below is a graphed comparison of the usage of the boy name Sly and related names. The only popular variation form of Sly (#unlisted) ranked in the Top 1000 is Sylvester. Adoption of this boy name reached its highest during the years 1890-1899 and is now significantly less, with the form Sylvester becoming less in vogue. (2014 Birth Statistics)