A more thorough explanation:

Definition: A Pinkerton is a slang term used to refer to a private detective or security guard who is usually armed. The name comes from the Pinkerton Detective Agency, which was the first private detective agency in the United States and was established in 1852.

Example: The company hired a Pinkerton to investigate the theft of their confidential documents.

Explanation: In this example, the term Pinkerton is used to refer to a private detective who was hired by the company to investigate the theft of their confidential documents. The Pinkerton is expected to use his skills and expertise to uncover the culprit and recover the stolen documents.

Example: The Pinkertons were notorious for their involvement in the labor disputes of the late 19th and early 20th centuries.

Explanation: This example illustrates the historical significance of the Pinkerton Detective Agency. The Pinkertons were known for their involvement in labor disputes, where they were often hired by companies to break up strikes and intimidate workers. This led to a negative reputation for the Pinkertons among labor unions and workers.