G-Men for Jimmy Hoffa Explained.

Don and Sal’s aliases as “G-Men” (J. Edgar Hoover’s slang for
“government men”) investigating Hoffa are in step with the time, as by
1963 Kennedy was almost certainly having the union leader’s accounts
shuffled through in hopes of finding an Al Capone loophole to put him
away for.

James Riddle Hoffa was a labor union leader; he served as General
President of the Teamsters union from 1958 until 1971. He attempted to
amass a number of trades into one union, including truck drivers,
airplane workers, and other transport employees. Kennedy grew
suspicious of him and had him investigated; in 1964 he was convicted
of attempted bribery.

His sentence was for 15 years but was commuted by President Nixon.
Hoffa was released from jail in 1971. In 1975, he disappeared
completely from a parking lot in Michigan. He was never heard from
again and is presumed dead.

• footnote - by Natasha Simons