turns out that the original "gumshoes" of the late 1800's were shoes or boots made of gum rubber, the soft-soled precursors of our modern sneakers... At the turn of the century "to gumshoe" meant to sneak around quietly as if wearing gumshoes, either in order to rob or, conversely, to catch thieves. "Gumshoe man" was originally slang for a thief, but by about 1908 "gumshoe" usually meant a police detective, as it has ever since.