G-Man (short for Government Man) is a slang term for Special agents of the United States Government. It is specifically used as a term for a Federal Bureau of Investigation (FBI) agent. In FBI mythology, the nickname is held to have originated during the arrest of gangster George "Machine Gun" Kelly by agents of the Bureau of Investigation (BOI), a forerunner of the FBI, in September 1933. Finding himself unarmed, Kelly supposedly shouted "Don't shoot, G-Men! Don't shoot, G-Men!". This event is dramatized in the 1959 film, The FBI Story, where its somewhat implausible quality is in no way diminished. The earliest cite in OED for the American usage (as opposed to the Irish, see below) is 1930 from a book on Al Capone by FD Pasley. http://en.wikipedia.org/wiki/G-Man_(slang)

Theres alot of G-man meaning if you try to search,the meaning that you gave is the exact or original meaning of it. For uncle sam well you got the meaning.. cowboy...

I have only heard it to refer to Federal agents, not state or local, and specifically back in the first half of the twentieth century when the federal government was fighting organized crimes. There were a lot of movies back then that had g-men in them. Uncle Sam is the government. I can say, "I don't want Uncle Sam restricting my internet access." I can not say "I'm from Uncle Sam. Nice to meet you."

uncle Sam = American government Uncle Sam is a common national personification of the American government originally used during the War of 1812. http://en.wikipedia.org/wiki/Uncle_Sam

Uncle Sam is the country. G-men are FBI agents.