Some federal agents still get a kick out of Hoffa's middle name. The R stands for Riddle. It was his mother's maiden name and might seem to be a fitting description of how his life ended.
Hoffa's apparent evaporation from Earth has become one of the nation's greatest whodunits and also the frequent feed for sick jokes.
The former, powerful Teamster's Union boss is synonymous with things that cannot be found, people who cannot be identified, newly poured freeways and freshly groomed football stadiums.
But there is really no mystery about Hoffa's sudden departure, according to one FBI agent who worked the case.
"Hoffa's kidnapping and murder was motivated largely by personal vendetta," says Joe Brennan, a career FBI agent and organized crime squad supervisor assigned to Detroit and Newark as well as Chicago - all key locations in the Hoffa case. Brennan is now a top private sleuth with a large Chicago investigative firm.
Then-New Jersey Teamster official and organized crime boss Anthony "Tony Pro" Provenzano, according to Brennan, ordered the grudge killing. That conclusion is based on information provided to the FBI by Mafia informants and is included in Hoffa's secret, voluminous FBI files.
Provenzano's role in Hoffa's disappearance has been reported over the years. But his motive has always been presumed to be a union-related, checkmate-murder designed to block Hoffa's Teamster comeback.
"Hoffa was trying to get back into labor even though he was told not to" by the courts, says Brennan. "Information we got was that the mob was concerned that his re-entry was going to create investigative interest in union activities which could cause problems" for the mob.
"Provenzano saw a great opportunity to exact revenge" under the cover of a preventive union move, says Brennan. "So, he launched a couple of his guys" to eradicate Hoffa.
But in remarkable candor 26 years after one of America's most daring crimes, Brennan reveals the truth behind the Hoffa disappearance.
Hoffa's gangland termination had nothing to do with his second ascension to the Teamsters throne, but everything to do with Anthony Provenzano's blood feud with Hoffa.
The planned retaliation germinated from the time that both he and Hoffa were serving time in the same federal prison, according to Brennan.
"He and Jimmy had done time together in Pennsylvania in the late 1960s and '70s," said Brennan. The FBI's information was that "Hoffa didn't show the appropriate respect for a made (Mafia) guy in prison."
In short, Brennan says Hoffa didn't kiss Provenzano's Cosa Nostra ring while both were at the Lewisburg penitentiary. So, years later, Tony Pro wrung
Hoffa's neck. "It got to the point where Provenzano indicated that one day he'd have his measure of revenge."
That day was July 30, 1975. Hoffa had left his house in suburban Detroit for a luncheon meeting at a fancy restaurant. He told his wife Josephine that he would be home by 4 p.m. to char some steaks for dinner.
The steaks were never cooked.
Instead, after high noon, Hoffa was snatched from his car in the parking lot of the Machus Red Fox Restaurant in well-heeled Bloomfield Hills.
Brennan says the FBI was told by mob informants that Jersey enforcer Salvatore "Sally Bugs" Briguglio and a lesser-known wheelman grabbed Hoffa and took him on his final ride.
"He wanted to see the body," says Brennan. The "he" was Tony Provenzano, whose jailhouse tiff with Hoffa had festered for years.
"We were told that Hoffa was grabbed, killed there (Detroit) and brought back to New Jersey for Provenzano to personally verify that he was dead."
Brennan says that mob informants told federal agents Hoffa was rubbed out and his remains stuffed into a 55-gallon oil drum. The drum was put on a truck and driven to New Jersey for Provenzano's eyeball inspection.
Ironically, behind the wheel of the makeshift funeral procession, would have been a driver reaping the benefits of Hoffa- generated Teamster's contracts.
Once Hoffa's stout corpse made it to New Jersey, federal agents suspect that Provenzano merrily popped the drum lid to see his old prison mate. There was Hoffa's head, said the FBI informant, delivered beneath a platter.
"That's where it ended," recalls Brennan of the information provided by the FBI's mob snitch. Hoffa was "either melted into the Meadowlands" sports stadium in New Jersey "or dumped into the Atlantic."
Hoffa was declared dead in 1982, but because his body was never found, the FBI case technically remains open. Because of that, Brennan says, FBI reports that back up the informants' story will stay classified.
And Anthony "Tony Pro" Provenzano won't be doing any tell-all autobiography. Provenzano died during a subsequent prison stay.
The man the FBI figures killed Hoffa, Sal Briguglio, died in a gangland hit. A few years after Hoffa's liquidation, "Sally Bugs" himself took a revolver-full of bullets in the mouth outside a mob nightclub in New York. That was "a tremendous message to anybody" not to talk about Hoffa, says Brennan.
But the FBI knows who did what to Jimmy Hoffa. They'll just never have the body of a man whose middle name will forever be his legacy: Riddle.