_Etymology of Slang_ (Vol. vii., p. 331.).--
"SLANGS are the greaves with which the legs of convicts are fettered,
having acquired that name from the manner in which they were worn, as
they required a sling of string to keep them off the ground.... The
irons were the _slangs_; and the slang-wearer's language was of course
slangous, as partaking much if not wholly of the
_slang_."--_Sportsman's Slang, a New Dictionary and Varieties of Life_,
by John Bee: Preface, p. 5.