No pussy-footing around with metaphors

In order to walk silently while plodding against the nefarious, enforcers eschewed leather soles in favor of rubber-based shoebottoms. Shoes based with the slightly translucent rubber-gum were said (by extension) to be "gumshoes." By further extension, the shoes made the person into a "gumshoe."

At first issued to uniformed police, they were retained for use when some became detectives, and somehow over the years came to be the shoe of choice -- and for a time, the sobriquet -- of private detectives.

Today, "gumshoe" is pretty much old hat in the USA. When the official term became Private Investigator, gumshoe gave way to "P.I." and "Private Eye" (from the I-nitial of "Investigator").

Originally posted by David Moody of La La land