What does the "G" mean in "G-Man"?

The "G" in "G-man" stands for "Government." The term originated in the 1930s and referred to the special agents working for various government agencies, primarily the Federal Bureau of Investigation (FBI). These agents were given the moniker "G-men" due to their affiliation with the Government and their involvement in law enforcement activities. The term has since been popularized through various forms of media, representing the authority and power of government agents in carrying out their duties.