Gumshoe (noun)

A private investigator or detective.

Origin:

The word gumshoe is a slang term for a private investigator or detective, likely derived from the phrase "to walk on gumshoes" meaning to walk quietly or stealthily.

Examples:

1. He hired a gumshoe to follow his wife and find out if she was having an affair.
2. The gumshoe followed the suspect for days before finally getting the evidence needed for the arrest.
3. In the film noir, the gumshoe is a hard-boiled detective who solves crimes.
4. The gumshoe was skilled at getting people to talk and reveal information.
5. The gumshoe used a variety of techniques to track down the missing person.